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Title: Cast Forming of Carbon Nanotube Networks Using Paraffin.
Creator: Veliky, Kenneth, Department of Industrial and Manufacturing Engineering
Abstract/Description: Carbon nanotube thin film, or buckypaper, is one of the most revolutionary materials in the 21st century. Mechanical, electrical, and thermodynamic properties that can only be dreamed of in science fiction novels are now within reach in the science and technology field. As amazing as this material is, there exist problems within the manufacturability of buckypaper. Problems such as process time, scalability, and cost effectiveness to produce a sample hinder the ability to produce buckypaper...
Show moreCarbon nanotube thin film, or buckypaper, is one of the most revolutionary materials in the 21st century. Mechanical, electrical, and thermodynamic properties that can only be dreamed of in science fiction novels are now within reach in the science and technology field. As amazing as this material is, there exist problems within the manufacturability of buckypaper. Problems such as process time, scalability, and cost effectiveness to produce a sample hinder the ability to produce buckypaper to the commercial market. This research effort is to study, through experimentation, a new approach to create buckypaper using cast formation of a carbon nanotube network while in a paraffin suspension. Because current nanotube dispersion and filtration methods, such as sonication can produce high costs and slow processing times, the need for new buckypaper manufacturing method is evident. During this experiment, buckypaper was created using two methods for dispersion, the first was a mechanic mixing method and the second was the traditional method of sonication. The study proves that the use of paraffin as the dispersion and flow medium does not provide ideal results to eliminate steps such as sonication and filtration. The resultant buckypaper through mixing did not yield good results due to the nature of carbon nanotube's tendency to agglomerate while heat is applied during the dispersion process. Poor dispersion leads to a decrease in functional properties such as mechanical, electrical or thermodynamic. It is conclusive that further investigation into this method is necessary.
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Date Issued: 2014
Identifier: FSU_migr_uhm-0361
Format: Thesis

Title: Biocompatible Poly (Lactic Acid)/Thermoplastic Polyurethane Blends.
Creator: Burkett, Mary K., Department of Industrial and Manufacturing Engineering
Abstract/Description: In order to create a polymer that has the morphology and structure to be used for industrial applications, the foamability of the PLA must be improved by blending. Blends were made in specific ratios of 80/20, 50/50, and 20/80. Next, the blends were extruded and injected into molds for testing. The mechanical and thermal properties of the blends were tested using the tensile test and the DSC. The morphology was also observed using the SEM. Finally, a series of stock materials were created to...
Show moreIn order to create a polymer that has the morphology and structure to be used for industrial applications, the foamability of the PLA must be improved by blending. Blends were made in specific ratios of 80/20, 50/50, and 20/80. Next, the blends were extruded and injected into molds for testing. The mechanical and thermal properties of the blends were tested using the tensile test and the DSC. The morphology was also observed using the SEM. Finally, a series of stock materials were created to be used for melt-electrospinning or 3D printing.
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Date Issued: 2015
Identifier: FSU_migr_uhm-0526
Format: Thesis

Title: A Study on Sonication Dispersion Parameters for Batchproduction of Carbon Nanotube Buckypaper.
Creator: Vargas, Emily Anne, Department of Industrial and Manufacturing Engineering
Abstract/Description: Buckypaper (BP) is a macroscopic aggregate of carbon nanotubes. More specifically, it is an easy-to-handle thin film formed from carbon nanotube networks. Buckypaper contains valuable high mechanical strength, electrical, and thermal conductivity due to their nanoscale dimension and unique structural network. Application examples of buckypaper include for fire and lightning protection, aerospace structures, armor plating, artificial muscles, miniaturization of electrical connections, and etc....
Show moreBuckypaper (BP) is a macroscopic aggregate of carbon nanotubes. More specifically, it is an easy-to-handle thin film formed from carbon nanotube networks. Buckypaper contains valuable high mechanical strength, electrical, and thermal conductivity due to their nanoscale dimension and unique structural network. Application examples of buckypaper include for fire and lightning protection, aerospace structures, armor plating, artificial muscles, miniaturization of electrical connections, and etc. The current batch-production method has its own associated limitations and problems, including long process time, cost effectiveness, as well as spilling and improper sonication operation. This research will focus on the analysis of sonication time, examining an effective filtration model that will produce buckypaper at effective rates, and the effect of oven drying on the buckypaper, without sacrificing its conducive, electric, and strength properties. The technical approach used in this work is to study the effect of varying the sonication process time on the quality and properties of the resultant buckypaper samples. During this experiment, buckypaper was created using high, medium, and low sonication times, as well as samples were placed in the oven and compared to those that were not. The study proves that lower sonication time does not prove to be ideal in the maintaining the properties of the buckypaper. The resultant buckypaper did not yield good results due to the tendency of carbon nanotubes to agglomerate with short sonication dispersion time. Additionally, samples that were not placed in the oven after water and methanol baths still proved to have large amounts of surfactant left over, affecting the density and properties of the buckypaper. Poor dispersion and high residual surfactant lead to a decrease in functional properties such as mechanical, electrical, and thermodynamic of the buckypaper. Further investigation into applying those batch-production parameters to the continuous manufacturing process is necessary.
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Date Issued: 2015
Identifier: FSU_migr_uhm-0585
Format: Thesis

Title: Interfacial Bonding Property Study of Functionalized Cnt Nanocomposites Based on a Modified Cox's Model.
Creator: Wang, Xianping, Liang, Richard, Wang, Ben, Okoli, Okenwa, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Many researchers have studied the interfacial shear stress (ISS) in nanocomposites through theoretical calculation, computational simulation or sophisticated nanomanipulation experiment measurement. In this research, we attempt to directly calculate ISS values in actual nanocomposites based on a modified Cox's model using tensile test results of various macroscopic carbon nanotube (CNT) nanocomposites. Young's modulus, tensile strength and strain of CNT ropes rather than individual CNT...
Show moreMany researchers have studied the interfacial shear stress (ISS) in nanocomposites through theoretical calculation, computational simulation or sophisticated nanomanipulation experiment measurement. In this research, we attempt to directly calculate ISS values in actual nanocomposites based on a modified Cox's model using tensile test results of various macroscopic carbon nanotube (CNT) nanocomposites. Young's modulus, tensile strength and strain of CNT ropes rather than individual CNT properties were applied into the model. The effects of functionalization, CNT rope length, volume fraction and CNT type (SWNT, DWNT, MWNT) on interfacial shear stress were studied. It was found that the functionalization increased the mechanical properties of both interfacial bonding and DWNT and MWNT rope themselves; however, it decreased the mechanical properties of SWNT ropes. The major failure mode of the CNT nanocomposites was identified to be CNT rope rupture. The calculation results revealed that the ISS values in the nanocomposites are comparable with the ones reported in literature.
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Date Issued: 2010
Identifier: FSU_migr_etd-1252
Format: Thesis

Title: Elastic Property Prediction and Variation Quantification for Buckypaper-Polymer Nanocomposites: Modeling and Experimental Validation.
Creator: Tsai, Chao-hsi, Zhang, Chuck, Oates, William, Wang, Ben, Vanli, O. Arda, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: A practical method to utilize carbon nanotubes (CNTs) in structural applications is to fabricate them into buckypapers (BPs), a thin film containing two-dimensional CNT networks, and combine them with a polymer matrix to make BP-polymer (BPP) composites. It has been demonstrated that BPP composites have very good mechanical properties with multi-functional capabilities. However, due to the uncertainties involved in different manufacturing stages, the resulting BPP composites exhibit larger...
Show moreA practical method to utilize carbon nanotubes (CNTs) in structural applications is to fabricate them into buckypapers (BPs), a thin film containing two-dimensional CNT networks, and combine them with a polymer matrix to make BP-polymer (BPP) composites. It has been demonstrated that BPP composites have very good mechanical properties with multi-functional capabilities. However, due to the uncertainties involved in different manufacturing stages, the resulting BPP composites exhibit larger property variations when compared with traditional metal or ceramic materials. As such, there is need for an improved modeling strategy that can provide rapid property predictions and variation quantifications for BPP composites through measurable buckypaper nanostructures and processing conditions. Due to high material costs and long production cycle times, it is nearly impossible to construct a statistical-based model for BPP composites purely from physical experiments. Theoretical (micromechanical) models are more cost effective, but they also have some drawbacks. Namely, they are computationally intensive, deterministic in nature, and have questionable accuracy due to underlying simplified assumptions. Different sources of variations in BPP composite manufacturing also build on the inadequacy of these micromechanical models for providing reasonable predictions without further adjustments. Therefore, the main objective of this study is to provide a better modeling strategy for the prediction of BPP composite stiffness. By integrating a series of statistical methods with traditional micromechanical models, the variations observed in different stages were quantified, and a better predictive surrogate modeling strategy was constructed as a result. The statistical dispersions of buckypaper nanostructures (nanotube bundle length, diameter, orientation and waviness) were first analyzed and characterized by applying image analysis to microscopic images of buckypaper surface. It was found that the distribution of bundle length and diameter can be reasonably described by a two-parameter Weibull distribution, and the orientation of nanotubes can be represented by a periodic Fourier series. A stochastic based model was then constructed to predict the theoretical dispersions of BPP composite stiffness through experimentally measured nanostructure distributions by combining micromechanics with a Monte-Carlo simulation. It was found that the distribution of BP nanostructures would bias the resultant BPP composite modulus if a non-symmetric nanostructure distribution was present. The degree of nanostructure effects and interactions was analyzed using polynomial modeling and sensitivity analysis. The diameter and waviness of nanotube bundles were found to be the most influential factors for BPP composite modulus in most cases. The intra/inter buckypaper variations were studied using an Analysis of Variance (ANOVA) test. Both variations were tested as insignificant and can thus be statistically combined using the "mean nanostructure distribution" with pooled mean and variance. Lastly, two different sets of BPP composite experiments were used to validate the predictive capability of the constructed model. Preliminary results exhibited a noticeable discrepancy between theoretical predictions and physical observations due to the imperfections of the CNT-polymer interface. Therefore, statistical two-stage sequential modeling was applied to calibrate the original micromechanical model, and the resultant surrogate model was demonstrated to possess improved predictive capabilities. Recently functionalized BPP composite data also showed a very good correspondence to the theoretical predictions after the CNT-polymer interface was improved.
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Date Issued: 2010
Identifier: FSU_migr_etd-1500
Format: Thesis

Title: Dielectric and Mechanical Properties of PMMA/BTA Nanocomposites for HTS Applications.
Creator: Ingrole, Aniket, Liang, Zhiyong Richard, Rodrigo, Horatio, Okoli, Okenwa, Zhang, Mei, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: To prepare dielectric materials for High Temperature Superconductor (HTS) cables, nanocomposites consisting of Polymethylmethacrylate (PMMA) and Barium Titanate (BTA) nanoparticles have been manufactured and evaluated. The main objective of this research is to enhance the dielectric breakdown strength and reduce the dielectric losses of the nanocomposites. Polymethylmethacrylate (PMMA) with the addition of BTA (5wt.% and 10wt.% ) nanocomposites were fabricated by using two different methods....
Show moreTo prepare dielectric materials for High Temperature Superconductor (HTS) cables, nanocomposites consisting of Polymethylmethacrylate (PMMA) and Barium Titanate (BTA) nanoparticles have been manufactured and evaluated. The main objective of this research is to enhance the dielectric breakdown strength and reduce the dielectric losses of the nanocomposites. Polymethylmethacrylate (PMMA) with the addition of BTA (5wt.% and 10wt.% ) nanocomposites were fabricated by using two different methods. The breakdown voltage measurements have been conducted under AC, DC and lightning impulse high voltage. The measurements were conducted at both room temperature (293 K) and liquid nitrogen temperature (77 K). The results of the electrical breakdown field measurements of the nanocomposites are compared with those of the base polymer. Fracture surface analysis was carried out with SEM analysis. The difference in the breakdown area due to different modes of voltages applied and effect of the nanoparticles was studied. Mechanical characterization of the resultant nanocomposites was also carried out at both the room temperature (293K) and at cryogenic temperature (77K). The effects of nanoparticles on the electrical and mechanical properties were observed. A marginal increase in the dielectric strength of the nanocomposites was observed for AC conditions at both the temperatures. There was a decrease in the values of nanocomposites for impulse conditions. At cryogenic temperature nanocomposites showed higher dielectric strength when DC voltage was applied. For both the temperatures, dielectric losses increased as the voltage was increased for all the materials studied, except for PMMA/10wt.%BTA nanocomposites at cryogenic temperature, which showed decrease of losses by ~ 70%. An increase of ~12% in Young's modulus and ~ 65% increase in tensile strength of the nanocomposites were observed at cryogenic temperature. It also shows that more material damage was observed under AC breakdown voltage compared to the impulse and DC voltage breakdown cases. Also the material damage was more pronounced at 77 K than that at 293 K.
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Date Issued: 2010
Identifier: FSU_migr_etd-3865
Format: Thesis

Title: Short Carbon Nanotubes and Carbon Nanofibers Composites: Fabrication and Property Study.
Creator: Koo, Ana, Liang, Zhiyong Richard, Liu, Tao, Zhang, Chun Chuck, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Carbon nanotubes (CNTs) have drawn interest for many applications since their discovery. While they provide exceptional mechanical, physical and chemical properties, several technical barriers must be overcome before these properties can be fully used. Some of such drawbacks concern length control, lack of good dispersion and poor interfacial bonding. Currently, CNTs such as single-walled carbon nanotubes (SWNTs) and multi-walled carbon nanotubes (MWNTs) and carbon nanofibers (CNFs) are...
Show moreCarbon nanotubes (CNTs) have drawn interest for many applications since their discovery. While they provide exceptional mechanical, physical and chemical properties, several technical barriers must be overcome before these properties can be fully used. Some of such drawbacks concern length control, lack of good dispersion and poor interfacial bonding. Currently, CNTs such as single-walled carbon nanotubes (SWNTs) and multi-walled carbon nanotubes (MWNTs) and carbon nanofibers (CNFs) are produced in lengths ranging between several to hundreds micrometers and are usually bounded into macroscopically entangled networks. This contradicts with the requirements of some applications, which in the end will benefit with short and highly dispersed CNTs in lengths of a few hundred nanometers or less, such as drug delivering and energy storage carriers. Short CNTs (s-CNTs) and CNFs (s-CNFs) can enhance the mechanical properties of a composite due to the increased interaction with the polymer matrix, through the improvement of the interfacial bonding and resin encapsulation, which is possible with existing open ends of nanotubes. Ultimately this influences the matrix's properties by affecting its chain entanglements, morphology, and crystallinity in the nanocomposite. This research is a continuous effort on nanoscale cutting and characterization of s-CNTs and s-CNFs. Moreover, this research used s-MWNTs and s-CNFs in the lengths of 200 and 500 nm to manufacture the nanocomposites. The mechanical properties of the resultant nanocomposties were characterized. The interactions of the s-MWNT and s-CNTs with epoxy resin matrix were observed using high-resolution SEM and atomic-resolution TEM. The results were compared to nanocomposites with pristine MWNTs and CNFs. In the study, four case studies were explored: 1) 200 nm s-MWNT/epoxy composites; 2) 500 nm s-MWNTs/epoxy composites; 3) 200 nm s-CNF/epoxy composites; 4) 500 nm s-CNF/epoxy composites. For all four cases the MWNT and CNF concentrations were 0.05 wt%, 0.10 wt%, and 1.00 wt%, respectively. Significant mechanical improvements were observed. The strength of the s-MWNT nanocomposite at 1.00 wt% gave a 64% improvement compared to the control sample. The highest young's modulus was also obtained in the 1.00 wt% s-MWNT (200 nm) nanocomposite, and it showed an increase of 44%. In general, the most significant improvements were seen with the s-MWNTs (200 nm) nanocomposites due to their smaller diameters and shorter length. Glass transition temperature was also studied. Finally, the interfacial bonding and interactions of the nanotube's opened ends with the resin matrix were observed through HR-SEM and atomic-resolution TEM analysis, which validated the creation of MWNT and CNF opened ends and the actual resin encapsulation inside the nanotubes' hollow structures.
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Date Issued: 2011
Identifier: FSU_migr_etd-2841
Format: Thesis

Title: Feasibility Study of Radio-Frequency (RF) Inductor Energy Harvesting.
Creator: Braimah, Ibrahim, Owusu, Yaw A., Awoniyi, Samuel A., Weatherspoon, Mark H., Okoli, Okenwa I., Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: As wireless devices become more prevalent, the radio frequency (RF) spectrum is becoming more densely populated with cell phone and internet related broadband activities (e.g. text messaging, web browsing, and wireless routing). This feasibility study presents a sensitivity study on how location, use of an antenna and motion may impact the ability to measure RF power density for specific frequencies. The RF power obtained from a nearby radio station was compared to the relative RF power...
Show moreAs wireless devices become more prevalent, the radio frequency (RF) spectrum is becoming more densely populated with cell phone and internet related broadband activities (e.g. text messaging, web browsing, and wireless routing). This feasibility study presents a sensitivity study on how location, use of an antenna and motion may impact the ability to measure RF power density for specific frequencies. The RF power obtained from a nearby radio station was compared to the relative RF power available for frequencies understudy. The results of the study indicated that 2.4 GHz is significant in terms of prevalence and power density which allows for technological opportunity and caution due to potential health hazards. Optimization of a 2D inductor is also presented and which makes it easier for RF inductor designers to selectively choose the dimensions and number of turns of the inductor based on the desired inductance and power.
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Date Issued: 2007
Identifier: FSU_migr_etd-3408
Format: Thesis

Title: Experimental Study and Modeling of Nanotube Buckypaper Composite Actuator for Morphing Structure Applications.
Creator: Tsai, Szu-Yuan, Liang, Zhiyong, Oates, William, Wang, Ben, Zhang, Chuck, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: The objectives of this research are to develop lightweight high-performance nanotube composite actuators that can be operated in open air and to study their actuation mechanisms. We successfully demonstrated solid electrolyte-based buckypaepr actuators. Long MWNT and dopped SWNT BP actuators showed significant improvement of actuation performance. A constitutive structure-stimulation-performance model has been developed to analyze and predict actuation performance. The modeling results can be...
Show moreThe objectives of this research are to develop lightweight high-performance nanotube composite actuators that can be operated in open air and to study their actuation mechanisms. We successfully demonstrated solid electrolyte-based buckypaepr actuators. Long MWNT and dopped SWNT BP actuators showed significant improvement of actuation performance. A constitutive structure-stimulation-performance model has been developed to analyze and predict actuation performance. The modeling results can be further used to improve the actuation performance through parameter studies. Lightweight all-solid-state nanotube composite actuators developed in this research were a bimorph configuration with a high conductive solid electrolyte layer sandwiched by two nanotube buckypaper electrode layers. The effects of driving voltages and frequencies were studied. The nanotube buckypaper composite actuators demonstrated consistent responses to electrical stimulation frequencies up to 40 Hz. Different types of nanotube buckypapers were tested to determine their actuation performance, including randomly dispersed single-walled carbon nanotubes (SWNT), aligned SWNT, randomly dispersed multi-walled carbon nanotubes (MWNT), randomly dispersed long MWNT and SWNT-MWNT mixed nanotube buckypapers. Dynamic mechanical analysis (DMA) and tensile tests were conducted to determine actuator mechanical properties. A Young's modulus of 2.17 GPa from long MWNT buckypaper composite actuator was one of the highest reported values among electro-active polymer composite actuators. The research also realized significant performance improvements by using long MWNT nanotube buckypapers and lithium ion doped SWNT buckypapers as electrode layers. The resultant actuators can achieve more than 20 mm displacements, which is about 10 times greater than untreated SWNT buckypaper composite actuators. Ionic doped SWNT buckypaper actuators are especially promising because they consume 70% less power to perform the same amount of actuation compared to long MWNT buckypaper actuators. The maximum strain and blocking force of the long MWNT BP composite actuators were 0.77% and 8.7 mN, respectively. The research indicated two actuation mechanisms of nanotube buckypaper actuators co-exist: 1) carbon-carbon (C-C) bond extensions when an electrical charge applied, as previously reported in the literature, and 2) an ionic current flow effect in the solid electrolytes. The developed structure-stimulation-performance model was able to predict the displacement of nanotube buckypaper actuators based on both mechanisms. Modeling results indicate that ionic current flow effect was the dominant effect in the devices. By conducting parameter studies, we can reveal the influential factors for actuation performance. The modeling results for the SWNT BP/Nafion actuator were in good agreement with experimental data. The resultant actuators are promising for lightweight morphing structure applications.
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Date Issued: 2010
Identifier: FSU_migr_etd-1504
Format: Thesis

Title: Piezoresistivity of Mechanically Drawn Swcnt Thin Films: Mechanism and Optimizing Principle.
Creator: Obitayo, Waris, Liu, Tao, Shanbhag, Sachin, Zhang, Mei, Okoli, Okenwa, Oates, William S., Florida State University, College of Engineering, Department of Industrial and...
Show moreObitayo, Waris, Liu, Tao, Shanbhag, Sachin, Zhang, Mei, Okoli, Okenwa, Oates, William S., Florida State University, College of Engineering, Department of Industrial and Manufacturing Engineering
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Abstract/Description: Carbon nanotubes (CNTs) are known to exhibit outstanding mechanical, electrical, thermal, and coupled electromechanical properties. CNTs can be employed towards the design of an innovative strain sensor with enhanced multifunctionality due to their load carrying capability, sensing properties, high thermal stability, and outstanding electrical conductivity. All these features indicate the prospect to use CNTs in a very wide range of applications, for instance, highly sensitive resistance-type...
Show moreCarbon nanotubes (CNTs) are known to exhibit outstanding mechanical, electrical, thermal, and coupled electromechanical properties. CNTs can be employed towards the design of an innovative strain sensor with enhanced multifunctionality due to their load carrying capability, sensing properties, high thermal stability, and outstanding electrical conductivity. All these features indicate the prospect to use CNTs in a very wide range of applications, for instance, highly sensitive resistance-type strain/force sensors, wearable electronics, flexible microelectronic devices, robotic skins, and in-situ structural health monitoring. CNT-based strain sensors can be divided into two different types, the individual CNT- based strain sensors and the ensemble CNT-based strain sensors e.g. CNT/polymer nanocomposites and CNT thin films. In contrast, to individual CNT-based strain sensors with very high gauge factor (GF) e.g. ~3000, the ensemble CNT-based strain sensors exhibit very low GFs e.g. for a SWCNT thin film strain sensor, GF is ~1. This research discusses the mechanisms and the optimizing principles of a SWCNT thin film piezoresistive sensor, and provide an experimental validation of the numerical/analytical investigations. The dependence of the piezoresistivity on key parameters like alignment, network density, bundle diameter (effective tunneling area), and SWCNT length is studied. The tunneling effect is significant in SWCNT thin films showing higher degrees of alignment, due to greater inter-tube distances between the SWCNTs as compared to random oriented SWCNT thin films. It can be concluded that SWCNT thin films featuring higher alignment would have a higher GF. On the other hand, the use of sparse network density which comprises of aligned SWCNTs can as well intensify the tunneling effect which can result to a further increase in the GF. In addition, it is well-known that percolation is greatly influenced by the geometry of the nanotubes e.g. bundle diameter and length. A study on the influence of bundle diameter of SWCNTs on the piezoresistivity behavior of mechanically drawn SWCNT thin films showed the best performance with an improved GF of ~10 when compared to the randomly oriented SWCNT thin films with GF of ~1. The non-linear piezoresistivity of the mechanically drawn SWCNT thin films is considered to be the main mechanism behind the high strain sensitivity. Furthermore, information about the average length and length distribution is very essential when examining the influence of individual nanotube length on the strain sensitivity. With that in mind, we use our previously developed preparative ultracentrifuge method (PUM), and our newly developed gel electrophoresis and simultaneous Raman and photolumiscence spectroscopy (GEP-SRSPL) to characterize the average length and length distribution of SWCNTs respectively.
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Date Issued: 2015
Identifier: FSU_2015fall_Obitayo_fsu_0071E_12891
Format: Thesis

Title: Hierarchy Generation for Designing Assembly System for Product with Complex Liaison and Sub-Assembly Branches.
Creator: Jiang, Zhengqian, Wang, Hui, Okoli, Okenwa, Vanli, Omer Arda, Florida State University, FAMU-FSU College of Engineering, Department of Industrial and Manufacturing Engineering
Abstract/Description: Manufacturers need to deploy their assembly systems in a timely manner to cope with expedited product development. Design of such responsive assembly systems consists of generation of assembly/subassembly operations and their hierarchies, operation-machine assignment, selections of machine types and quantities, and the material flow among machines. Exploration of all the feasible solutions to the assembly operations and their hierarchical relationships is vital to optimization of system...
Show moreManufacturers need to deploy their assembly systems in a timely manner to cope with expedited product development. Design of such responsive assembly systems consists of generation of assembly/subassembly operations and their hierarchies, operation-machine assignment, selections of machine types and quantities, and the material flow among machines. Exploration of all the feasible solutions to the assembly operations and their hierarchical relationships is vital to optimization of system designs. This research developed a theoretical framework based on a recursive algorithm to automatically generate all feasible and non-redundant assembly hierarchies efficiently, thereby investigating its impact on assembly system designs. Then this research further discussed the potential applications of the recursive framework in system optimization including joint determination of optimal assembly operations, operation-machine assignment, machine types and quantities, and the material flows among machines. The work was also extended to the optimization of assembly systems for the products with complex liaison relations and product families.
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Date Issued: 2015
Identifier: FSU_2015fall_Jiang_fsu_0071N_12971
Format: Thesis

Title: Morphology and Properties of Polymer/Carbon Nanotube Nanocomposite Foams Prepared by Supercritical Carbon Dioxide.
Creator: Hossieny, Nemat, Zeng, Changchun, Liang, Zhiyong, Liu, Tao, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Poly(methyl methacrylate) (PMMA) multi-walled carbon nanotubes (MWCNTs) nanocomposites were synthesized by several methods using both pristine and surface functionalized carbon nanotubes (CNTs). Fourier transform infrared (FTIR) spectroscopy was used to characterize the presence and types of functional groups in functionalized CNTs, while the dispersion of CNTs in PMMA was characterized using scanning electron microscopy (SEM). The prepared nanocomposites were foamed using carbon dioxide (CO2...
Show morePoly(methyl methacrylate) (PMMA) multi-walled carbon nanotubes (MWCNTs) nanocomposites were synthesized by several methods using both pristine and surface functionalized carbon nanotubes (CNTs). Fourier transform infrared (FTIR) spectroscopy was used to characterize the presence and types of functional groups in functionalized CNTs, while the dispersion of CNTs in PMMA was characterized using scanning electron microscopy (SEM). The prepared nanocomposites were foamed using carbon dioxide (CO2) as the foaming agent. The cell morphology was observed by SEM, and the cell size and cell density were calculated via image analysis. It was found that both the synthesis methods and CNTs surface functionalization affect the CNTs dispersion in the polymer matrix, which in turn profoundly influences the cell nucleation mechanism and cell morphology. The CNTs are efficient heterogeneous nucleation agents leading to increased cell density at low particle concentrations. A mixed mode of nucleation mechanism was observed in nanocomposite foams in which polymer rich and particle rich region co-exist due to insufficient particle dispersion. This leads to a bimodal cell size distribution. Uniform dispersion of CNTs can be achieved via synergistic combination of improving synthesis methodology and CNT surface functionalization. Foams from these nanocomposites exhibit single modal cell size distribution and remarkably increased cell density and reduced cell size. An increase in cell density of ~70 times and reduction of cell size of ~80% was observed in nanocomposite foam with 1% CNTs. The effect of CNT surface functionalization on the tensile properties of the PMMA/MWNT nanocomposite and nanocomposite foams were noticed. An increase of ~60% in elastic modulus and ~40% increase in the tensile strength was observed in nanocomposite foam with 0.5 % functionalized CNTs.
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Date Issued: 2010
Identifier: FSU_migr_etd-3742
Format: Thesis

Title: Efficient Mixed-Level Fractional Factorial Designs: Evaluation, Augmentation and Application.
Creator: Guo, Yong, Simpson, James R., Niu, Xufeng, Awoniyi, Samuel A., Pignatiello, Joseph J., Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: In general, a minimum aberration criterion is used to evaluate fractional factorial designs. This dissertation begins with a comprehensive review and comparison of minimum aberration criteria definitions regarding their applications, relationships, advantages, limitations and drawbacks. A new criterion called the general balance metric, is proposed to evaluate and compare mixed-level fractional factorial designs. The general balance metric measures the degree of balance for both main effects...
Show moreIn general, a minimum aberration criterion is used to evaluate fractional factorial designs. This dissertation begins with a comprehensive review and comparison of minimum aberration criteria definitions regarding their applications, relationships, advantages, limitations and drawbacks. A new criterion called the general balance metric, is proposed to evaluate and compare mixed-level fractional factorial designs. The general balance metric measures the degree of balance for both main effects and interaction effects. This criterion is related to, and dominates orthogonality criteria as well as traditional minimum aberration criteria. Besides, the proposed criterion provides immediate feedback and comprehensively assesses designs and has practical interpretations. The metric can also be used for the purpose of design augmentation to improve model fit. Based upon the proposed criterion, a method is proposed to identify the optimal foldover strategies for efficient mixed-level designs. The analysis of mixed-level designs involving qualitative factors can be achieved through indicator variables or contrast coefficients. A regression model is developed to include qualitative factor interactions which have been previously ignored.
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Date Issued: 2006
Identifier: FSU_migr_etd-3910
Format: Thesis

Title: Construction of Efficient Fractional Factorial Mixed-Level Designs.
Creator: Guo, Yong, Simpson, James R., Awoniyi, Samuel A., Pignatiello, Joseph J., Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Mixed-level factorial designs are experimental designs whose factors have different numbers of levels. These designs are very useful in experiments involving both qualitative and quantitative factors. One design approach is to run all possible combinations of the factor levels. However, as the number of factors or factor levels increases, the number of experiments increases dramatically. As a result, research has focused on developing orthogonal or near-orthogonal fractional factorial designs...
Show moreMixed-level factorial designs are experimental designs whose factors have different numbers of levels. These designs are very useful in experiments involving both qualitative and quantitative factors. One design approach is to run all possible combinations of the factor levels. However, as the number of factors or factor levels increases, the number of experiments increases dramatically. As a result, research has focused on developing orthogonal or near-orthogonal fractional factorial designs. The property of design balance, that the same number of runs is performed for each factor level, has been maintained in currently proposed designs. In some cases, maintaining balance requires too many experimental runs. The objective of this thesis is to develop fractional mixed-level factorial designs with economical run size that have desirable properties associated with near-balance and near-orthogonality. Two criteria are developed to assess the degree of near-balance for comparing and constructing designs. A modified J2-optimality criterion is used for comparing design near-orthogonality. These criteria are combined to assess different design alternatives. A genetic algorithm is then used to build designs with the most desirable combination of near-balance and near-orthogonality.
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Date Issued: 2003
Identifier: FSU_migr_etd-3911
Format: Thesis

Title: Fully Printable Single Layer Halide Perovskite/Peo Composite Thin Film LEDs.
Creator: Bade, Sri Ganesh Rohit, Yu, Zhibin, Liang, Zhiyong Richard, Wang, Hui, Florida State University, College of Engineering, Department of Industrial and Manufacturing Engineering
Abstract/Description: Traditional light emitting diodes (LEDs) involve a complicated device structure with multiple layers stacked over one another. Such a complex, multilayered architecture restricts the application of diverse fabrication techniques. Earth-abundant organometal halide perovskites (Pero) have been well astounded for their appealing optoelectronic properties, low cost and solution processability which make them ideal candidates for large size photovoltaic and LED applications. The objective of this...
Show moreTraditional light emitting diodes (LEDs) involve a complicated device structure with multiple layers stacked over one another. Such a complex, multilayered architecture restricts the application of diverse fabrication techniques. Earth-abundant organometal halide perovskites (Pero) have been well astounded for their appealing optoelectronic properties, low cost and solution processability which make them ideal candidates for large size photovoltaic and LED applications. The objective of this thesis work is to fabricate Pero LED with uniform surface morphology, eliminating the multilayers with the help of Pero/Polyethylene oxide (PEO) composite thin film. Because of the simplicity in device architecture, this novel approach has the potential to surpass all the conceivable troubles involved in the fabrication of Pero LEDs. Preliminary results show a working device achieved by spin coating a thin film of Pero/PEO composite on ITO/glass serving as a bottom electrode and with In/Ga as the top electrode. Furthermore, fully printable and flexible Pero LEDs can be developed from this approach which can be scaled to large commercial roll to roll manufacturing.
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Date Issued: 2016
Identifier: FSU_2016SU_Bade_fsu_0071N_13351
Format: Thesis

Title: Laser Processing for Manufacturing Nanocarbon Materials.
Creator: Van, Hai Hoang, Zhang, Mei, Li, Hui, Okoli, Okenwa, Liang, Zhiyong Richard, Liu, Tao, Florida State University, FAMU-FSU College of Engineering, Department of Industrial and...
Show moreVan, Hai Hoang, Zhang, Mei, Li, Hui, Okoli, Okenwa, Liang, Zhiyong Richard, Liu, Tao, Florida State University, FAMU-FSU College of Engineering, Department of Industrial and Manufacturing Engineering
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Abstract/Description: CNTs have been considered as the excellent candidate to revolutionize a broad range of applications. There have been many method developed to manipulate the chemistry and the structure of CNTs. Laser with non-contact treatment capability exhibits many processing advantages, including solid-state treatment, extremely fast processing rate, and high processing resolution. In addition, the outstanding monochromatic, coherent, and directional beam generates the powerful energy absorption and the...
Show moreCNTs have been considered as the excellent candidate to revolutionize a broad range of applications. There have been many method developed to manipulate the chemistry and the structure of CNTs. Laser with non-contact treatment capability exhibits many processing advantages, including solid-state treatment, extremely fast processing rate, and high processing resolution. In addition, the outstanding monochromatic, coherent, and directional beam generates the powerful energy absorption and the resultant extreme processing conditions. In my research, a unique laser scanning method was developed to process CNTs, controlling the oxidation and the graphitization. The achieved controllability of this method was applied to address the important issues of the current CNT processing methods for three applications. The controllable oxidation of CNTs by laser scanning method was applied to cut CNT films to produce high-performance cathodes for FE devices. The production method includes two important self-developed techniques to produce the cold cathodes: the production of highly oriented and uniformly distributed CNT sheets and the precise laser trimming process. Laser cutting is the unique method to produce the cathodes with remarkable features, including ultrathin freestanding structure (~200 nm), greatly high aspect ratio, hybrid CNT-GNR emitter arrays, even emitter separation, and directional emitter alignment. This unique cathode structure was unachievable by other methods. The developed FE devices successfully solved the screening effect issue encounter by current FE devices. The laser-control oxidation method was further developed to sequentially remove graphitic walls of CNTs. The laser oxidation process was directed to occur along the CNT axes by the laser scanning direction. Additionally, the oxidation was further assisted by the curvature stress and the thermal expansion of the graphitic nanotubes, ultimately opening (namely unzipping) the tubular structure to produce GNRs. Therefore the developed laser scanning method optimally exploited the thermal laser-CNT interaction, successfully transforming CNTs into 2D GNRs. The solid-state laser unzipping process effectively addressed the issues of contamination and scalability encountered by the current unzipping methods. Additionally, the produced GNRs were uniquely featured with the freestanding structure and the smooth surfaces. If the scanning process was performed in an inert environment without the appearance of oxygen, the oxidation of CNTs would not happen. Instead, the greatly mobile carbon atoms of the heated CNTs would reorganize the crystal structure, inducing the graphitization process to improve the crystallinity. Many observations showing the structural improvement of CNTs under laser irradiation has been reported, confirming the capability of laser to heal graphitic defects. Laser methods were more time-efficient and energy-efficient than other annealing methods because laser can quickly heat CNTs to generate graphitization in less than one second. This subsecond heating process of laser irradiation was more effective than other heating methods because it avoided the undesired coalescence of CNTs. In my research, the laser scanning method was applied to generate the graphitization, healing the structural defects of CNTs. Different from the reported laser methods, the laser scanning directed the locally annealed areas to move along the CNT axes, migrating and coalescencing the graphitic defects to achieve better healing results. The critical information describing the CNT structural transformation caused by the moving laser irradiation was explored from the successful applications of the developed laser method. This knowledge inspires an important method to modify the general graphitic structure for important applications, such as carbon fiber production, CNT self-assembly process and CNT welding. This method will be effective, facile, versatile, and adaptable for laboratory and industrial facilities.
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Date Issued: 2015
Identifier: FSU_2016SP_Van_fsu_0071E_12881
Format: Thesis

Title: Modified Natural Fibrils for Structural Hybrid Composites: Towards an Investigation of Textile Reduction.
Creator: Ufodike, Chukwuzubelu O., Dickens, Tarik J., Zhang, Mei, Shrivastava, Abhishek Kumar, Chatterjee, Jhunu, Florida State University, FAMU/FSU College of Engineering, Department of...
Show moreUfodike, Chukwuzubelu O., Dickens, Tarik J., Zhang, Mei, Shrivastava, Abhishek Kumar, Chatterjee, Jhunu, Florida State University, FAMU/FSU College of Engineering, Department of Industrial and Manufacturing Engineering
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Abstract/Description: Recently, the interest for renewable resources for fibers particularly of plant origin has been increasing. Reduction of use of traditional textile materials is now considered more critical due to the increasing environmental concern. Natural fibers are renewable, biodegradable, recyclable, and lightweight materials with high specific modulus, in competition with man-made fossil materials and fiberglass. Natural fibers are used for preparation of functionalized textiles to achieve smart and...
Show moreRecently, the interest for renewable resources for fibers particularly of plant origin has been increasing. Reduction of use of traditional textile materials is now considered more critical due to the increasing environmental concern. Natural fibers are renewable, biodegradable, recyclable, and lightweight materials with high specific modulus, in competition with man-made fossil materials and fiberglass. Natural fibers are used for preparation of functionalized textiles to achieve smart and intelligent properties. However, the incorporation of these fibers in composite systems has been challenging due to their hydrophilic nature. Nevertheless, the fact that these biodegradable materials can be manipulated at a nano-scale to complement desired objective and application has made them a favorable option. The idea behind this project is to explore ways to convert green waste to high value materials and to utilize natural building blocks to design textile reinforcement materials. In this work, cellulose nanofibrils (CNF) supplied from the University of Maine were hydrophobized by silylation and characterized using Fourier-Transform Infrared (FTIR) spectroscopy, Raman spectroscopy, and Thermogravimetric analysis (TGA). Results from FTIR spectroscopy showed a formation of Si-O-C bonds, indicating better fiber-matrix adhesion. Raman spectroscopy showed disruption of hydrogen bonding which indicates interference of parallel nanocellulose fiber adhesion to neighboring fibrils. The TGA suggests that the thermal stability of the functionalized CNF is higher than that of the corresponding neat sample, which could be a result of stable Si bond formation. The raw materials (neat and functionalized) were encapsulated in a polystyrene matrix through a solvent and non-solvent precipitation process, and then extruded using single and dual heat processing. The extruded thin filaments were tested according to the ASTM D638 (tensile test of plastics). Results showed an increasing Ultimate Tensile Strength (UTS) and Elastic Modulus, with peak values attributed to the dual-heat processing up to 79% and 69% increase respectively at 5wt% loading. Further increase was seen at 10wt% loading up to 112MPa UTS, and modulus up to 10.7GPa for the dual-heat processing. The UTS increase is assumed to be a result of linear arrangement of CNF in the matrix during the extrusion process. The results revealed the strong reinforcing ability of CNF and their compatibility with thermoplastic matrix if functionalized.
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Date Issued: 2016
Identifier: FSU_2016SP_Ufodike_fsu_0071N_13186
Format: Thesis

Title: Topological and Electrical Properites of Carbon Nanotube Networks.
Creator: Li, Min-Yang, Liang, Zhiyong Richard, Park, Chiwoo, Andrei, Petru, Zhang, Mei, Florida State University, College of Engineering, Department of Industrial and Manufacturing...
Show moreLi, Min-Yang, Liang, Zhiyong Richard, Park, Chiwoo, Andrei, Petru, Zhang, Mei, Florida State University, College of Engineering, Department of Industrial and Manufacturing Engineering
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Abstract/Description: A major challenge to the study of the structure-property relationship of carbon nanotube (CNT) networks is to characterize the complex nanostructure with complicated nanoscale contacts and pore structures. An image-based characterization methodology was proposed to extract CNT network information directly from scanning electron microscope (SEM) images of various CNT thin films to characterize critical topological factors including bundle size, diameter, and orientation from the CNT networks....
Show moreA major challenge to the study of the structure-property relationship of carbon nanotube (CNT) networks is to characterize the complex nanostructure with complicated nanoscale contacts and pore structures. An image-based characterization methodology was proposed to extract CNT network information directly from scanning electron microscope (SEM) images of various CNT thin films to characterize critical topological factors including bundle size, diameter, and orientation from the CNT networks. This approach provided high-fidelity and fast analysis of CNT network structures with low false positive rate (FPR) of ~3% and ~90% accuracy in most of our case studies. We applied the new approach to study different networks of multi-walled carbon nanotube (MWNT), single-walled carbon nanotube (SWNT), MWNT-SWNT mixed, and stretched MWNTs with different CNT alignments, which revealed the electrical conductivity-structure relationships of MWNT networks. On the other hand, controlling the transfer of electrical and mechanical properties of nanotubes into nanocomposites remains one of the major challenges due to the lack of adequate measurement systems to quantify the variations in bulk properties while the nanotubes were used as the reinforcement material. One-way analysis of variance (ANOVA) on thickness and conductivity measurements were conducted. By analyzing the data collected from both experienced and inexperienced operators, we found some operation details users might overlook that resulted in variations, since conductivity measurements of CNT thin films are very sensitive to thickness measurements. In addition, we demonstrated how issues in measurements damaged samples and limited the number of replications resulting in large variations in the electrical conductivity measurement results. Based on this study, we proposed a faster, more reliable approach to measure the thickness of CNT thin films that operators can follow to make these measurement processes less dependent on operator skills.
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Date Issued: 2015
Identifier: FSU_2016SU_Li_fsu_0071E_13311
Format: Thesis

Title: Thermal Conductivity and Coefficients of Thermal Expansion of SWNTs/Epoxy Nanocomposites.
Creator: Gonnet, Philippe, Liang, Zhiyong, Brooks, James, Wang, Ben, Zhang, Chuck, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Since their discovery in 1991, carbon nanotubes have undergone intensive research. The single-walled carbon nanotube, or SWNT, has a unique electronic structure. According to their chirality, they can be either metallic or semiconductors with various band gaps. These different electronic structures influence their electrical and thermal properties. Studies have been conducted to understand, model and measure their electrical and thermal properties by computer simulation and experimental...
Show moreSince their discovery in 1991, carbon nanotubes have undergone intensive research. The single-walled carbon nanotube, or SWNT, has a unique electronic structure. According to their chirality, they can be either metallic or semiconductors with various band gaps. These different electronic structures influence their electrical and thermal properties. Studies have been conducted to understand, model and measure their electrical and thermal properties by computer simulation and experimental measurements. Even though current research shows inconsistent results, all studies show that SWNTs have phenomenal electrical and thermal properties. To take advantage of these unique properties of nanotubes requires properly incorporating SWNTs into a matrix as a reinforcement or filler to form nanocomposites with desired properties. Carbon nanotube reinforced composites are still under development. The mechanical properties of these materials have been intensively explored; however, the electrical and thermal properties still require further study. The main objective of this thesis was to measure and understand the thermal behavior of SWNT-reinforced composites. This thesis focuses on 1) the thermal conductivity of buckypapers (aligned or random SWNT network from filtration of well-dispersed nanotube suspension) and the nanocomposites produced from the buckypapers, and 2) the influence of nanotubes on thermal expansion by direct mixing and casting samples of SWNT/epoxy nanocomposites. Thermal conductivity was measured using a comparative method, with a constantan foil as a reference. The temperature dependence of the thermal conductivity was measured from 115 K to room temperature. Magnetically aligned buckypapers produced with 17.3 Tesla magnetic field showed the highest thermal conductivity at room temperature, with a maximum value of 41.5 W/mK in the aligned direction. The coefficient of thermal expansion (CTE) was measured using the Thermomechanical Analyzer (TMA). The influence of nanotube functionalization and loading on the CTE of the epoxies revealed that adding 1 wt% nanotubes in the epoxy resin could reduce the CTE of the resin as much as 35.5%. The mechanisms of thermal conductivity variation and CTE reduction in the buckypapers and nanocomposites are also discussed.
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Date Issued: 2004
Identifier: FSU_migr_etd-4142
Format: Thesis

Title: Design, Manufacture and Performance of Solar Powered Floating Fountaing.
Creator: Gomez, Eduardo J., Owusu, Yaw A., Roberts, Rodney, Simpson, James, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Photovoltaic (PV) systems behave in an extraordinary and useful way: they react to light by transforming part of the incoming photons into electricity. Since PV installations require no fuel to operate, produce no pollution while producing electricity, they require little maintenance and are modular. These unique properties make the technology a cost and energy-effective means of permitting a wide range of solar- electric applications. Thus, innovative design and manufacture of PV devices and...
Show morePhotovoltaic (PV) systems behave in an extraordinary and useful way: they react to light by transforming part of the incoming photons into electricity. Since PV installations require no fuel to operate, produce no pollution while producing electricity, they require little maintenance and are modular. These unique properties make the technology a cost and energy-effective means of permitting a wide range of solar- electric applications. Thus, innovative design and manufacture of PV devices and equipment, offers a new vision for consumers and business as to how power can be provided. One such application involves the design and manufacture of a Solar-Powered Floating Fountain, including a robust design of experiment, performance, cost and safety analyses, is presented in this thesis. The uniqueness of the fountain manufactured for this research is the capability for aeration of stagnant water bodies, such as lakes and ponds. Aeration of these water bodies by using solar power is not only a new application of the renewable energy, but also, it provides an affordable method to promote biodiversity in stagnant ponds and lakes. The fountain was built by the Research Center for Cutting-Edge Technologies (RECCET) and installed on a pond at Innovation Park, Tallahassee. The system is composed of two pumps, an air compressor, six solar panels, kit of batteries, a linear current booster, pressurized water tank and the float. Aeration was by exposing the water to air through the nozzles on the tank. By using this technique, the lake gained dissolved oxygen in the lowest layer, accomplishing the main objective of this project. Statistical analysis using a Split Plot design showed a significant uptake of both dissolved oxygen and destratification.
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Date Issued: 2006
Identifier: FSU_migr_etd-4152
Format: Thesis

Title: Carbon Nanotube Buckypaper Permeability and Prepreg Process Study.
Creator: Click, Bryant Marshall, Liang, Richard, Wang, Ben, Okoli, Okenwa, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Carbon nanotubes (CNTs) possess great potential for developing high-performance and multifunctional nanocomposites for a wide variety of applications. As the cost of producing CNT buckypaper, a thin film of CNT networks, continues to decrease while the quality increases, more users and companies are becoming interested in buckypaper for potential applications. Many of these applications, such as electromagnetic interference (EMI) shielding and fire retardant surface skins for fiber-reinforced...
Show moreCarbon nanotubes (CNTs) possess great potential for developing high-performance and multifunctional nanocomposites for a wide variety of applications. As the cost of producing CNT buckypaper, a thin film of CNT networks, continues to decrease while the quality increases, more users and companies are becoming interested in buckypaper for potential applications. Many of these applications, such as electromagnetic interference (EMI) shielding and fire retardant surface skins for fiber-reinforced composites or plastics, may not require buckypaper-based composites to be much stronger compared to fiber-reinforced composites. This means that there is a market for buckypaper even without its theoretical super strength, but desired functionality. There is however a number of challenges with the potential scale-up production of composite parts with affordable buckypaper materials usually made of low cost CNTs, such as multi-walled carbon nanotubes (MWNTs). Such buckypaper is usually very lightweight (10-25 g/m2), thin (10-20 microns), and fragile, hence even small variations and damage in the wet lay-up process can result in large quality variations in the final buckypaper composite. These variations include buckypaper volume fraction, resin rich areas, and contact between BP and other reinforcement materials etc. Thus, keeping the consistency of the resulting microstructure and quality of buckypaper composites is a very challenging issue. The objective of this project is to study nanostructure-permeability relationships of different types of buckypaper materials, and explore effective prepreg processes to make buckypaper composites with greatly increased consistency, quality, CNT weight fraction and uniformity in the resulting products. The experimental results show that buckypapers have very low permeability, about 8-12 orders lower than those of carbon fiber preform cases, and also sensitive to liquid polarity due to their nanoscale porosity and large surface area. Both solution and resin film transfer prepregging processes were studied to pre-impregnate buckypaper to achieve 50 wt. % CNT concentration. The late one showed better quality in the resultant nanocomposites, but difficult for high viscosity resins. Three case studies were also conducted to demonstrate quality and property consistency of buckypaper composites.
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Date Issued: 2010
Identifier: FSU_migr_etd-3581
Format: Thesis

Title: Characterization of the Blocking Force Generated by Buckypaper Composite Actuators.
Creator: Labrador, Daniel, Liang, Richard, Zhang, Chuck, Oates, William, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Lightweight composite actuators with large bending displacement and high blocking force have great potentials for various engineering applications. Carbon nanotube thin film or Buckypaper-based composite actuators (BCAs) have been developed and tested in an open air environment to demonstrate their use as electromechanochemical actuation devices. The actuator is a bimorph structure fabricated with Nafion, a solid electrolyte layer capable of ion diffusion, sandwiched between two buckypaper ...
Show moreLightweight composite actuators with large bending displacement and high blocking force have great potentials for various engineering applications. Carbon nanotube thin film or Buckypaper-based composite actuators (BCAs) have been developed and tested in an open air environment to demonstrate their use as electromechanochemical actuation devices. The actuator is a bimorph structure fabricated with Nafion, a solid electrolyte layer capable of ion diffusion, sandwiched between two buckypaper (BP) electrode layers. Actuation mechanisms were studied, revealing that ionic current flow is the major actuation mechanism. To further improve actuation performance, Nafion doping has been studied. LiCl and Imidazolium (IL) solutions have been used to dope the Nafion and both cases have demonstrated substantial increases of BCA displacement. With the dimensions of the BCA held constant(30 mm × 5 mm × 0.07 mm), a non-doped BCA with a 3 V stimulation input at 200 mHz only can generate a total bilateral displacement of up to 0.09 mm; but LiCl-doped and IL-doped BCAs can produce ×100 and ×150 more displacement than that of the non-doped BCAs, respectively. The effect of driving voltages and frequencies with respect to displacement and blocking force generation of IL-doped BCAs were characterized. BCA thickness variation was introduced to evaluate the effect of the BCA structure on actuation performance. The improved BCAs have achieved a maximum strain and stress of 0.1% and 0.175 MPa, respectively. This is comparable to other polymer-based actuators. Finally, a preliminary model of BCA blocking force estimation was proposed to predict and further optimize the BCA actuation properties. The predicted results of the model are in agreement with the experimental data.
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Date Issued: 2010
Identifier: FSU_migr_etd-3329
Format: Thesis

Title: Scalable Carbon Nanotube (CNT) Alignment: Process Development, Alignment Mechanisms and CNT/Carbon Fiber Hybrid Composite Applications.
Creator: Downes, Rebekah, Liang, Zhiyong (Richard), Vanli, Omer Arda, Spainhour, Lisa, Okoli, Okenwa, Maskell, Robin, Florida State University, College of Engineering, Department of...
Show moreDownes, Rebekah, Liang, Zhiyong (Richard), Vanli, Omer Arda, Spainhour, Lisa, Okoli, Okenwa, Maskell, Robin, Florida State University, College of Engineering, Department of Industrial and Manufacturing Engineering
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Abstract/Description: To transfer the incredible properties, including ultrahigh tensile strength, Young's modulus, and electrical conductivity of an individual carbon nanotube (CNT) into composite applications, the constituent nanotubes need to possess adequate alignment, interfacial bonding and a high CNT volume fraction. Direct incorporation of the CNT films, or buckypaper, materials into carbon fiber laminated structures to manufacture hybrid composites is an effective approach to utilize the lightweight,...
Show moreTo transfer the incredible properties, including ultrahigh tensile strength, Young's modulus, and electrical conductivity of an individual carbon nanotube (CNT) into composite applications, the constituent nanotubes need to possess adequate alignment, interfacial bonding and a high CNT volume fraction. Direct incorporation of the CNT films, or buckypaper, materials into carbon fiber laminated structures to manufacture hybrid composites is an effective approach to utilize the lightweight, conductive and nanostructured nature of dense CNT networks for multifunctional applications of structural carbon fiber composites. This work studied the microstructure-property relationships of CNT networks when orientation is induced. The mechanical stretching method is shown to be scalable and effective for ultra-high alignment. A manufacturing technique of applying a viscous resin treatment before the stretching procedure is shown to allow up to 80% stretching strain and a resultant alignment fraction of 0.93. The resin acts as an effective load transfer media to substantially enhance the ductility for high stretching strain. The alignment characterization is carried out through Raman spectroscopy and X-ray diffraction methods that reveal the graphitic crystal structure of the film. The load transfer mechanisms and failure modes of aligned CNT composites are explored through high concentration CNT reinforced nanocomposites. Atomic resolution transmission electron microscopy (TEM) analysis reveals unusual CNT crystal packing and permit the observation of interesting structural features of the CNTs and their assemblages, including collapse, flattened packing, preferred stacking, folding and twisting phenomena, as well as CNT pullouts from bundles and the resin matrix. The intimate surface-to-surface contact areas between aligned and flattened nanotubes, driven by van der Waals interactions, give rise to a high density packing of the flattened CNTs in the nanocomposite, resembling a graphitic crystal material. Molecular dynamics (MD) simulations were performed through collaboration to model the packing structure and understand the dependence of density on the relative content of flattened nanotube and void space. Macroscopic modeling predictions illustrate how the alignment and volume fraction of the encompassed CNTs affect the stiffness of the overall composite. CNT thin films were integrated into carbon fiber (CF) prepreg composites to create hybrid composite materials with high CNT content through industry standard autoclave fabrication processing. Resin bleeding along the through-thickness direction was inhibited due to extra-low permeability, nano/micro dual-scale flow characteristics and high resin absorbing capacity of the CNT thin film in hybrid composites. CNT swelling effects and resin starvation phenomena are studied in relation to the amount and orientation of the CNT laminates. The flexural three-point bending results of the random and aligned CNT/CF hybrids exhibit an increased resistance to catastrophic failure even under repeated loading parameters as compared to the CF control samples. The dramatic improvements in both in-plane and through-thickness electrical conductivities demonstrate potential for both structural and multifunctional applications of the resultant hybrid composites.
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Date Issued: 2015
Identifier: FSU_2015fall_Downes_fsu_0071E_12844
Format: Thesis

Title: Image Segmentation for Extracting Nanoparticles.
Creator: Allada, Kartheek, Park, Chiwoo, Shrivastava, Abhishek Kumar, Liu, Tao, Barbu, Adrian G. (Adrian Gheorghe), Florida State University, College of Engineering, Department of...
Show moreAllada, Kartheek, Park, Chiwoo, Shrivastava, Abhishek Kumar, Liu, Tao, Barbu, Adrian G. (Adrian Gheorghe), Florida State University, College of Engineering, Department of Industrial and Manufacturing Engineering
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Abstract/Description: With the advent of nanotechnology, nanomaterials have drastically improved our lives in a very short span of time. The more we can tap into this resource, the more we can change our lives for better. All the applications of nanomaterials depend on how well we can synthesize the nanoparticles in accordance with our desired shape and size, as they determine the properties and thereby the functionality of the nanomaterials. Therefore in this report, it is focused on how to extract the shape of...
Show moreWith the advent of nanotechnology, nanomaterials have drastically improved our lives in a very short span of time. The more we can tap into this resource, the more we can change our lives for better. All the applications of nanomaterials depend on how well we can synthesize the nanoparticles in accordance with our desired shape and size, as they determine the properties and thereby the functionality of the nanomaterials. Therefore in this report, it is focused on how to extract the shape of the nanoparticles from electron microscope images using image segmentation more accurately and more efficiently. By developing automated image segmentation procedure, we can systematically determine the contours of an assortment of nanoparticles from electron microscope images; reducing data examination and interpretation time substantially. As a result, the defects in the nanomaterials can be reduced drastically by providing an automated update to the parameters controlling the production of nanomaterials. The report proposes new image segmentation techniques that specifically work very effectively in extracting nanoparticles from electron microscope images. These techniques are manifested by imparting new features to Sliding Band Filter (SBF) method called Gradient Band Filter (GBF) and by amalgamating GBF with Active Contour Without Edges method, followed by fine tuning of μ (a positive parameter in Mumford-Shah functional). The incremental improvement in the performance (in terms of computation time, accuracy and false positives) of extracting nanoparticles is therefore portrayed by comparing image segmentation by SBF versus GBF, followed by comparing Active Contour Without Edges versus Active Contour Without Edges with the fusion of Gradient Band Filter (ACGBF). In addition we compare the performance of a new technique called Variance Method to fine tune the value of μ with fine tuning of μ based on ground truth, followed by gauging the improvement in the performance of image segmentation by ACGBF with fine tuned value of μ over ACGBF with an arbitrary value of μ.
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Date Issued: 2015
Identifier: FSU_2015fall_Allada_fsu_0071N_12975
Format: Thesis

Title: Stretchlon Film Enhanced Fabriaction of Nanocomposites with the Resin Infusion Between Double Flexible Tooling.
Creator: Bhakta, Divyesh, Okoli, Okenwa, Liang, Zhiyong (Richard), Dickens, Tarik J., Olawale, David O., Florida State University, FAMU-FSU College of Engineering, Department of...
Show moreBhakta, Divyesh, Okoli, Okenwa, Liang, Zhiyong (Richard), Dickens, Tarik J., Olawale, David O., Florida State University, FAMU-FSU College of Engineering, Department of Industrial and Manufacturing Engineering
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Abstract/Description: Recent studies have shown that the incorporation of carbon nanotubes (CNT) in to carbon fiber composite parts significantly increase mechanical as well as thermal properties. Polymer nanocomposites are polymer matrix composites that consist of reinforcements that have at least one dimension in the nanometer range. The polymer nanocomposite fabricated parts achieve greater mechanical, thermal, electrical and other properties with a low CNT reinforcement volume fraction. Nanocomposites achieve...
Show moreRecent studies have shown that the incorporation of carbon nanotubes (CNT) in to carbon fiber composite parts significantly increase mechanical as well as thermal properties. Polymer nanocomposites are polymer matrix composites that consist of reinforcements that have at least one dimension in the nanometer range. The polymer nanocomposite fabricated parts achieve greater mechanical, thermal, electrical and other properties with a low CNT reinforcement volume fraction. Nanocomposites achieve improved properties because of the higher properties of the nano-reinforcement and the high ratio of surface area to volume (aspect ratio) that provides greater interfacial interaction with the matrix. The fabrication of nanocomposites is primarily by the liquid composite molding (LCM) processes that can be complex process with many challenges. These challenges include poor CNT dispersion, poor bonding between resin and CNT, and blocking or filtration during the infusion process. The Resin Infusion between Double Flexible Tooling (RIDFT) however offers some advantages over the other LCM processes. The preservation and extended use of the mold can result in higher productivity and profit. In addition, a significantly lower pressure that translates to lower equipment cost, will be required to drive the high viscosity CNT-rich resin through the two-dimensional flow in a RIDFT process compared to the three-dimensional flow in the RTM. The RIDFT process may also be used for out-of-autoclave fabrication of composites from pre-pregs. The RIDFT process however has a number of fabrication issues militating against its wide use. These include long production cycle time due to the bottle neck associated with the setup time for cleaning the silicone sheet and the high cost of replacement of the flexible silicone membranes of the RIDFT machine. The introduction of Stretchlon Bagging 800 film may reduce the time that is expended on cleaning the silicone sheets and at the same time reduce the damage that is made to the silicone membranes. The goal of this thesis is to evaluate the performance of the Stretchlon bagging technique with the RIDFT process with the aim of significantly reducing the production cycle time as well as the production cost of composites and nanocomposites without adversely affecting the mechanical properties of the fabricated parts. The results show that the use of the Stretchlon bagging film resulted in reduction in the production cycle time of GFRP and CNT_GFRP parts of 32% and 42% respectively. It also resulted in production set-up (mold preparation) cost reduction for GFRP and CNT-GFRP parts of 49% and 72% respectively. It resulted in increased durability and service life of the silicon mold thereby helping to reduce the production cost. In addition, the use of the Stretchlon bagging film did not adversely affect the mechanical properties of the fabricated GFRP and CNT-GFRP parts. It resulted in an increase of 31.94% and 12.62% in the mean UTS of the GFRP and CNT-GFRP respectively. The Stretchlon film however resulted in reduction in the flexural properties of the fabricated GFRP and CNT-GFRP parts by 30.12% and 18.69% respectively. The use of the Stretchlon bagging film enhanced the in-plane properties of the fabricated parts by helping to increase the fiber volume fraction. The lower resin contents in the parts fabricated with the Stretchlon film may have had an adverse effect in the interlaminar properties resulting in lower flexural strengths. Furthermore, thermal analysis confirmed that there was no change in the glass transition (Tg) temperature of the fabricated parts. Parts fabricated with the Stretchlon bagging film also exhibited better surface finish than those fabricated without using the Stretchlon bagging film. In addition, a new design for the RIDFT with higher pressure capability for better quality parts (higher fiber volume fraction and lower void content) fabrication has been made. The new design also incorporates infrared lamp system for expedited curing of the composite parts in order to reduce the cycle time. Further work is however needed to optimize the RIDFT-Stretchlon film fabrication process for nanocomposites. A more detailed microscopy study needs to be performed to gain better insights into the reasons for the enhanced fiber volume content and in-plane properties achieved with the use of the Stretchlon film. In addition, the study needs to be repeated with functionalized CNTs to study the effects of functionalized CNTs on the fabricated parts, the silicon mold and the Stretchlon film. There is also the need to fabricate the new RIDFT design and optimize its performance for nanocomposite fabrication.
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Date Issued: 2015
Identifier: FSU_2015fall_Bhakta_fsu_0071N_12806
Format: Thesis

Title: Preparation and Characterization of Magnetically Aligned Carbon Nanotube Buckypaper and Composite.
Creator: Shankar, Kadambala Ravi, Liang, Zhiyong, Wang, Ben, Zhang, Chuck, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Carbon nanotubes are theoretically one of the strongest and stiffest materials with a calculated tensile strength of ~200 giga Pascal and modulus of more than 1-4 tera Pascal for a single walled nanotube (SWNT). If the mechanical properties of SWNT could be effectively incorporated into a polymer matrix, composites with lightweight, exceptional strength and stiffness can be achieved. The effective utilization of nanotubes in composites for applications depends on the ability to disperse the...
Show moreCarbon nanotubes are theoretically one of the strongest and stiffest materials with a calculated tensile strength of ~200 giga Pascal and modulus of more than 1-4 tera Pascal for a single walled nanotube (SWNT). If the mechanical properties of SWNT could be effectively incorporated into a polymer matrix, composites with lightweight, exceptional strength and stiffness can be achieved. The effective utilization of nanotubes in composites for applications depends on the ability to disperse the nanotubes uniformly throughout the matrix. Carbon nanotubes are anisotropic in nature. Therefore to take advantage of the nanotubes in the axial direction, controlled tube orientation or degree of alignment of nanotubes in the polymer matrix is very important to realize their high mechanical and functional properties. The nanocomposites produced by current conventional methods using direct mixing, melt blending or solution casting have failed to yield significant improvements in composite modulus. Although tremendous progress has been made towards understanding the properties of individual carbon nanotubes, but attaining the true potential of the bulk polymeric nanocomposites have been hindered by the lack of uniform SWNT dispersion, poor interfacial bonding, inadequate tube loading and uncontrollable tube orientation or degree of alignment. This thesis work developed an innovative approach for producing nanocomposites that has uniform SWNT dispersion, high tube loading and most importantly controlled tube orientation. In this research, these properties in composites were achieved by using magnetically aligned buckypapers and resin infusion system. The aligned nanotube buckypaper and composite were characterized using AFM and SEM. The mechanical properties of these materials were experimentally determined using DMA and were theoretically verified. The electrical properties of these materials were also experimentally determined using 4-probe resistivity measurements. Significant tube alignment has been achieved in the resultant buckypaper and nanocomposites. It is shown that the developed method is an effective way for producing nanocomposites with uniform SWNT dispersion desired tube alignment and high tube loading.
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Date Issued: 2003
Identifier: FSU_migr_etd-3403
Format: Thesis

Title: A Statistical Analysis of Effects of Test Methods on Spun Carbon Nanotube Yarn.
Creator: Veliky, Kenneth Blake, Liang, Zhiyong Richard, Zhang, Mei, Vanli, Omer Arda, Florida State University, College of Engineering, Department of Industrial and Manufacturing...
Show moreVeliky, Kenneth Blake, Liang, Zhiyong Richard, Zhang, Mei, Vanli, Omer Arda, Florida State University, College of Engineering, Department of Industrial and Manufacturing Engineering
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Abstract/Description: Carbon nanotube (CNT) fibers are very promising materials for many applications. Strong interactions among individual CNTs could produce a dense yarn results in exceptional properties. These properties are used in the application of high-performance reinforcement for composites. As the reinforcement, the primary function is to provide outstanding load bearing capability. Currently literatures use a variety of measurement techniques and gauge lengths that have not been uniform for CNT yarn...
Show moreCarbon nanotube (CNT) fibers are very promising materials for many applications. Strong interactions among individual CNTs could produce a dense yarn results in exceptional properties. These properties are used in the application of high-performance reinforcement for composites. As the reinforcement, the primary function is to provide outstanding load bearing capability. Currently literatures use a variety of measurement techniques and gauge lengths that have not been uniform for CNT yarn tests. The need for a standardized testing method for characterization is necessary in generating reproducible and comparable data for CNT yarn or fiber materials. In this work, the strength of CNT fibers was characterized using three different types of tensile test method: the film and fiber test fixtures from dynamics mechanic analysis (DMA), and TS 600 tensile fixture. Samples that underwent the film and TS 600 tensile fixture were attached with a thick paper tabbing methodology based on ASTM standard D3379. As for the fiber fixture was performed with the test material attached directly to the fixture based on the fiber test instruction from TA Instrument. The results of the three different methods provided distinct variance in stress, strain, and modulus. A design of experiment (DoE) was established and performed on the DMA film fixture as determined from the preliminary experiment. The DoE was successful in quantifying the critical parameters' ranges that attributed to standard deviation of average stress. These parameters were then tested on 30 more samples with an improved additive manufactured tab. The results significantly decreased all mechanical testing parameters' standard deviations. Most importantly, the results prove the probability of a valid gauge break increased to more than 400%.
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Date Issued: 2015
Identifier: FSU_2015fall_Veliky_fsu_0071N_12979
Format: Thesis

Title: Auxetic Polyurethane Foam: Manufacturing and Processing Analysis.
Creator: Jahan, Md. Deloyer, Zeng, Changchun, Liang, Zhiyong, Vanli, Arda, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Materials with negative Poisson's ratio are referred to as auxetic materials. They are different from conventional materials in their deformation behavior when responding to external stresses. The cross-section of the materials widens in the lateral direction when being stretched in the longitudinal direction and becomes narrower when being compressed longitudinally. While a number of natural auxetic materials exist, most auxetic materials are synthetic. They show interesting properties and...
Show moreMaterials with negative Poisson's ratio are referred to as auxetic materials. They are different from conventional materials in their deformation behavior when responding to external stresses. The cross-section of the materials widens in the lateral direction when being stretched in the longitudinal direction and becomes narrower when being compressed longitudinally. While a number of natural auxetic materials exist, most auxetic materials are synthetic. They show interesting properties and have potential in several important applications. Auxetic materials exhibit better mechanical properties than conventional materials such as enhanced indentation resistance, shear resistance, toughness, damping and energy absorption capacity, sound absorption, variable permeability and capability of producing complex curvature. These properties are beneficial in a wide range of applications including personal protective equipments, sound absorbers, packaging, smart filtration, drug delivery, tissue scaffolding, seat cushioning, etc. A wide range of auxetic materials has been synthesized. They include different polymers, metals, composites and ceramics. Among these, auxetic polyurethane (PU) foam is one of the most widely studied types of auxetic materials. Auxetic PU foams are usually fabricated by altering the microstructure of conventional foams and the unusual mechanical properties originate from the deformation characteristics of the microstructures. Three most important processing parameters in fabricating auxetic PU foam that dictate auxetic behavior are processing temperature, heating time and volumetric compression ratio. This study addresses several important issues in the manufacturing and characterization of auxetic PU foam. First, an improved automatic measuring technique has been developed to determine Poisson's ratio of auxetic PU foam. The technique involves development of a Matlab based image processing program. The second part of the study includes an experimental design approach to identify significant processing parameters followed by optimization of those processing parameters in fabrication of auxetic PU foam. A split-plot factorial design has been selected for screening purpose. Response Surface Methodology (RSM) has been utilized to optimize the processing parameters in fabrication of auxetic PU foam. Two different designs named Box-Behnken and I-optimal designs have been employed for this analysis. The results obtained by those designs exhibit that I-optimal design provides more accurate and realistic results than Box-Behnken design when experiments are performed in split-plot manner. Finally, a near stationary ridge system is obtained by optimization analysis. As a result a set of operating conditions are obtained that produces similar minimum Poisson's ratio in auxetic PU foam.
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Date Issued: 2014
Identifier: FSU_migr_etd-9011
Format: Thesis

Title: Modeling, Manufacturing, and Characterization of Nanocomposites and Multiscale Composites.
Creator: Kim, Myungsoo, Okoli, Okenwa I., Shanbhag, Sachin, Park, Young-Bin, Liang, Zhiyong, Jack, David, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Carbon nanotubes (CNTs) have excellent mechanical, electrical, and thermal properties making them outstanding reinforcements in polymer matrix composites. In this research, the effect of CNT-integration in polymer matrices (two-phase) and fiber-reinforced composites (three-phase) was studied theoretically and experimentally. This work sought to enhance the mechanical properties of composites by the improving dispersion of CNTs in polymers. This was achieved by optimizing the CNT/polymer...
Show moreCarbon nanotubes (CNTs) have excellent mechanical, electrical, and thermal properties making them outstanding reinforcements in polymer matrix composites. In this research, the effect of CNT-integration in polymer matrices (two-phase) and fiber-reinforced composites (three-phase) was studied theoretically and experimentally. This work sought to enhance the mechanical properties of composites by the improving dispersion of CNTs in polymers. This was achieved by optimizing the CNT/polymer composite manufacturing process. Generally, higher sonication intensity and longer sonication time improved the mechanical properties of CNT/polymer composites through improved CNT dispersion. Simulations for CNT/polymer composites (nanocomposites) and CNT/fiber/polymer composites (multiscale composites) were successfully carried out using a new method that combines nanocomposites micromechanics and woven fiber micromechanics. With this new method, the mechanical properties, including the Young's modulus, Poisson's ratio, and shear modulus, of nanocomposites and multiscale composites were predicted in terms of CNT loading in a polymer. The relationships between the mechanical properties of the composites and aspect ratios of the CNTs were studied and, as the third part of the simulation, the mechanical properties of multiscale composites that have no CNTs in the fiber strands were compared with those of multiscale composites that have CNTs in the fiber strands. In order to compare the predicted mechanical properties obtained by the simulations, nano and multiscale composites were manufactured and characterized. Good dispersion of the CNTs and strong bonding between the CNTs and polymer matrix and fibers and matrix are necessary to improve the mechanical properties of nanocomposites and multiscale composites.
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Date Issued: 2009
Identifier: FSU_migr_etd-3069
Format: Thesis

Title: Development of Integrated Process Design Environment and Statistical Analysis of RTM Process.
Creator: Li, Jing, Zhang, Chuck, Okoli, Okenwa, Liang, Zhiyong, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: The resin transfer molding (RTM) process has been used in the composite industry for decades. However, several issues still exist and impede its wide applications. Some design tools for RTM parts have been developed but a more efficient design environment is lacking. Race-tracking is a common phenomenon that makes prediction in actual production difficult and makes current deterministic optimal tooling design unrepeatable. This thesis integrates flow simulation and cost analysis modules...
Show moreThe resin transfer molding (RTM) process has been used in the composite industry for decades. However, several issues still exist and impede its wide applications. Some design tools for RTM parts have been developed but a more efficient design environment is lacking. Race-tracking is a common phenomenon that makes prediction in actual production difficult and makes current deterministic optimal tooling design unrepeatable. This thesis integrates flow simulation and cost analysis modules together with database management system (DBMS) providing a prototype of the integrated design environment for RTM processes. Preform permeability, especially race-tracking permeability that significantly affects not only simulated but also experimental results, was the factor being investigated. This thesis introduces a statistical approach utilizing statistically distributed variables to explain the race-tracking permeability values. One-dimensional flow experiments were conducted to obtain the permeability values. Three types of distribution (gamma distribution, Weibull distribution and lognormal distribution) were chosen as candidates. Experimental data were fitted for the three distributions. A goodness-of-fit test was performed to find the one that best describes the experimental data. Taking into account the fact that the severe levels of race-tracking can be represented by statistically distributed variables, this thesis proposes an optimization approach to minimize the sensitivity of the mold design to uncertainty of race-tracking permeabilities by choosing the appropriate locations of gates and vents (robust tooling design). A sensitivity that indicates the process robustness was defined as objective and evaluated by RTMSim software both for 2D and 2.5D geometry. With the conclusion that the ratios of race-tracking permeability over average values can be described by Weibull distributed variables, a random number generator was employed to generate the input race-tracking permeability data for obtaining values of the objective. Locations of vents were determined via the assumption that vents should be assigned at the locations where flow ends to avoid dry spot formation. Locations of gate were optimized from most possible locations.
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Date Issued: 2003
Identifier: FSU_migr_etd-3081
Format: Thesis

Title: The High Current-Carrying Capacity of Various CNT Enhanced Composites.
Creator: Azamian, Pegah, Liang, Richard Zhiyong, Zhang, Chuck, Zheng, Chad, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Carbon fiber reinforced composites (CFRPs) are light weight, have high strength and modulus, which make them qualified candidates for numerous automotive and aerospace industries. However one of the major technical challenges for these materials in airplanes bodies, in terms of aircraft safety and durability, is lightning strike protection (LSP). This is due to the inadequate electrical properties of normal CFRPs. Although, CFRPs have relatively good in-plane electrical conductivity compared...
Show moreCarbon fiber reinforced composites (CFRPs) are light weight, have high strength and modulus, which make them qualified candidates for numerous automotive and aerospace industries. However one of the major technical challenges for these materials in airplanes bodies, in terms of aircraft safety and durability, is lightning strike protection (LSP). This is due to the inadequate electrical properties of normal CFRPs. Although, CFRPs have relatively good in-plane electrical conductivity compared to neat epoxy resin, they lack metal-like high conductivity for LSP applications. To solve this issue, metal materials such as copper or aluminum mesh are attached to carbon fiber composites in the aircraft's body. This solution is not satisfactory due to heavy weight of metals and the occurrence of galvanic corrosion between metals and CFRPs. On other hand carbon nanotubes (CNTs) possess great potential for enhancing high-performance and multifunctional nanocomposites and exhibit incredible mechanical, electrical and thermal properties, which can replace the metal mesh materials. This study investigates the use of carbon nanotubes to enhance composite conductivity for potential metal material replacement and their basic current- carrying capacity. During testing, the samples were exposed to high temperatures with electrical current-induced thermal heating in atmosphere condition. High electrical currents generated Joule heating causing thermal degradation at over 600 °C (main failure mechanism). Micro-structural changes of the samples after electrical current heating were observed using SEM and EDS analyses. The result show resin evaporation at the notch and nucleation of Fe and Ti particles. CNTs enhance the current carrying capability of the CFRP and Buckypaper (preformed thin CNT film) composites. However, the performance improvement differs upon on the epoxy used as well as the manufacturing method and nantubes types. In addition higher conductivity of the samples contributed to higher current-carrying density at the breakdown point. These results provide a preliminary understanding of the effect of the CNTs on the current carrying capability and the electrical properties of CNT enhanced CFRPs and BP composites.
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Date Issued: 2010
Identifier: FSU_migr_etd-0268
Format: Thesis

Title: Computerization and Automation of Affordable Traffic Data Collection System for the State of Florida.
Creator: Mantena, Sitaramaraju, Spainhour, Lisa K., Owusu, Yaw A., Okoli, Okenwa I., Pignatiello, Joseph J., Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: The Florida Department of Transportation has initiated and funded development of electronic crash and citation reporting in Florida using the TraCS (Traffic and Criminal Software) platform. The TraCS system is application software that is a customizable data collection system that can be used by law enforcement and motor vehicle agencies to collect crash data. TraCS is combined with laptop computers, one or more personal computers (PC) in a central office. Peripherals such as image/bar code...
Show moreThe Florida Department of Transportation has initiated and funded development of electronic crash and citation reporting in Florida using the TraCS (Traffic and Criminal Software) platform. The TraCS system is application software that is a customizable data collection system that can be used by law enforcement and motor vehicle agencies to collect crash data. TraCS is combined with laptop computers, one or more personal computers (PC) in a central office. Peripherals such as image/bar code scanners and mobile printers, and data communications are in conjunction with TraCS to provide officers with all of the functionality needed to record and retrieve incident information wherever and whenever an incident occurs. The thesis objectives were to perform time study analysis and to investigate costs of current and proposed (TraCS-based) methods. The TraCS software was developed, and in the summer of 2003; seven Florida law enforcement agencies were selected to pilot and test electronic crash and citation reporting. The agencies were provided with required equipment and training to use TraCS software. The ride-alongs were performed with Jacksonville Sheriff's Office and Leon County Sheriff's Office (two of the pilot agencies). During the ride-alongs, the time taken to complete forms both with and without TraCS software was measured and the data analysis was performed. The study shows that the efficiency and accuracy of Florida traffic records was improved by using the electronic data collection system (TraCS). Data analysis showed that it takes less time to fill a crash report using TraCS compared to filling out a crash report manually on a paper form. On an average for the two vehicle crashes the time saved by using TraCS software to fill long form, short form, and driver exchange form were 11.7%, 11.3% and 8.3%, respectively. The time to fill a citation form using TraCS software was reduced by 13.6% from the time without TraCS. The software had best application when used in conjunction with the magnetic stripe reader for Florida driver license. The efficiency of officer's using TraCS differs based on the learning curve, equipment provided, and mindset of an officer. After suitable training the time taken to complete a report should decrease even further.
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Date Issued: 2004
Identifier: FSU_migr_etd-2749
Format: Thesis

Title: Molecular Modeling of Nanotube Composite Materials: Interface Formation, Interfacial Strength, and Thermal Expansion.
Creator: Marietta-Tondin, Olivier, Liang, Zhiyong, Brooks, James, Wang, Ben, Zhang, Chuck, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Carbon nanotubes (CNTs) are one of the wonders of modern science. Discovered a little over 15 years ago, they have shown the research community an outstanding set of properties. In terms of mechanical properties, they exhibit extremely high young's modulus, which, coupled with a high strain to break, leads to unsurpassed strength to break. CNTs also demonstrate superior thermal conductivity, good electrical capacity and high thermal stability. In light of these properties, CNTs are expected...
Show moreCarbon nanotubes (CNTs) are one of the wonders of modern science. Discovered a little over 15 years ago, they have shown the research community an outstanding set of properties. In terms of mechanical properties, they exhibit extremely high young's modulus, which, coupled with a high strain to break, leads to unsurpassed strength to break. CNTs also demonstrate superior thermal conductivity, good electrical capacity and high thermal stability. In light of these properties, CNTs are expected to be introduced into a wide variety of new materials aimed at applications for various fields, such as high-performance composites, biological and chemical sensors, magnetic recording, nanoelectronic devices and flat panel displays. One such promising application is CNT-reinforced composite materials, exhibiting the possibility of outstanding mechanical properties. In practice, however, many reports indicate that nanocomposites are weaker or only slightly stronger than the neat resins. Several factors are believed to be the primary source of this discrepancy, namely poor nanotube dispersion in resin, inadequate alignment of the nanotubes, and weak interfacial bonding between nanotubes and resins. As a result, these have become crucial investigation issues for developing high-performance nanocomposites. In this dissertation, fundamental understanding of the interfacial phenomena between carbon nanotubes and polymer matrices are studied. Both molecular dynamics (MD) simulation, an effective approach to investigate nanoscale behaviors, and experimental investigation, are utilized to achieve this goal. First, we examine the interface formation phenomena between a Single Wall Carbon Nanotube (SWNT) and the resin, prior to curing, in the case of the Epon862 resin system. The MD simulation results outline the validity of some of the current theories, such as molecular migration and reduction of molecular mobility of the resin, while they seem to indicate some other mechanisms are not present in this resin system, such as molecular wrapping around the SWNTs. Second, existing MD simulation models of nanotube pullout are analyzed and modified to examine the energy of certain material systems more correctly, and to characterize interfacial shear strength in SWNT/polymer composites. The interfacial bonding and load transfer behaviors between the different SWNTs' configurations (open end, capped end, functionalized end) and three different matrices (polystyrene, polyethylene and Epon862) were examined using the modified models. The results of the modified models effectively reveal the effects of different tube configurations and resin matrices on the interfacial strength during a simulated pullout. Finally, we use MD simulation to investigate the coefficient of thermal expansion (CTE) of individual SWNTs, SWNT ropes, as well as SWNT nanocomposites. Experiments were also carried out in order to gain further insight in the results. It is found that, while the CTE of individual nanotubes is of low negative value, the CTE of the same tubes within a rope or a nanocomposite can significantly change. We also find that SWNTs can be utilized to tailor the CTE of the Epon862 resin system, depending on the functionalization of the SWNTs prior to their introduction in the resin. Finally, a new twisting vibration mode was revealed in SWNT ropes that should prove critical in further SWNT rope studies utilizing MD simulation.
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Date Issued: 2006
Identifier: FSU_migr_etd-2739
Format: Thesis

Title: In-Situ Triboluminescent Optical Fiber Sensor for Real-Time Damage Monitoring in Cementitious Composites.
Creator: Olawale, David Oluseun, Okoli, Okenwa I., Sobanjo, John O., Liu, Tao, Liang, Zhiyong, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Triboluminescent-based sensor systems have the potential to enable in-situ and distributed structural health monitoring of composite structures. Inability to effectively capture and transmit optical signals generated within opaque composites like concrete and carbon fiber reinforced polymers have however greatly limited their use. This problem has been solved by developing the bio-inspired in-situ triboluminescent optical fiber (ITOF) sensor. This sensor has the potential for wireless, in...
Show moreTriboluminescent-based sensor systems have the potential to enable in-situ and distributed structural health monitoring of composite structures. Inability to effectively capture and transmit optical signals generated within opaque composites like concrete and carbon fiber reinforced polymers have however greatly limited their use. This problem has been solved by developing the bio-inspired in-situ triboluminescent optical fiber (ITOF) sensor. This sensor has the potential for wireless, in-situ, real-time and distributed (WIRD) damage monitoring. Its integrated sensing (triboluminescent thin film) and transmission (polymer optical fiber) components convert the energy from damage events like impacts and crack propagation into optical signals that are indicative of the magnitude of damage in composites. Utilizing the triboluminescent (TL) property of ZnS-Mn, the ITOF sensor has been successfully fabricated. Key design parameters were evaluated to develop a sensor with enhanced damage sensing capability. Sensor's performance was then characterized with Raman spectroscopy, field emission scanning electron microscopy (FESEM) and dynamic mechanical analysis (DMA). Flexural tests were also carried out to evaluate the damage sensing performance of the sensor before integrating into unreinforced concrete beams to create triboluminescent multifunctional cementitious composites (TMCC) with in-situ damage monitoring capabilities like biological systems. Results show that the ZnS-Mn in the epoxy coating of the ITOF sensor does not degrade the thermo-mechanical properties of the composite system. Raman spectroscopy indicates that the ZnS-Mn crystals retained their physical and chemical properties after undergoing the sensor fabrication process. Enhanced side-coupling of TL signals from the ITOF coating into the polymer optical fiber (POF) was achieved with TL thin film coating on POF. This makes distributed sensing possible when the length of the POF is coated with TL thin film. A new approach to damage characterization using TL emission profiles was employed with the TMCC. Three modes of sensor excitation in the TMCC were identified indicative of sensor's ability to sense crack propagation through the beam even when not in contact with the crack. FESEM analysis indicated that fracto-triboluminescence was responsible for the TL signals observed at beam failure. The TL profile analysis promises to facilitate better understanding of crack propagation in composite structural materials.
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Date Issued: 2013
Identifier: FSU_migr_etd-7954
Format: Thesis

Title: Pmma Carbon Nanotube Nanocomposite Foams for Energy Dissipation Applications.
Creator: Kynard, Kristin, Zeng, Changchun, Okoli, Okenwa, Vanli, Arda, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Nanomaterials have attracted a great deal of research efforts due to the potential unprecedented properties these materials may provide. Carbon nanotubes (CNTs) are of particular interest because of their exceptional mechanical, thermal and electrical properties. The purpose of this research is to develop poly (methyl methacrylate) (PMMA) carbon nanotubes (CNTs) nanocomposite foams with improved energy dissipation capabilities (toughness). PMMA CNTs nanocomposites were first synthesized by...
Show moreNanomaterials have attracted a great deal of research efforts due to the potential unprecedented properties these materials may provide. Carbon nanotubes (CNTs) are of particular interest because of their exceptional mechanical, thermal and electrical properties. The purpose of this research is to develop poly (methyl methacrylate) (PMMA) carbon nanotubes (CNTs) nanocomposite foams with improved energy dissipation capabilities (toughness). PMMA CNTs nanocomposites were first synthesized by anti-solvent precipitation process (ASP). Nanocomposites with different CNTs concentrations were prepared. The dispersion of the CNTs in the polymer matrix was observed by scanning electron microscopy (SEM). Nanocomposite foams were prepared by a batch process using carbon dioxide as the foaming agent. The foaming was conducted from the retrograde phase that enabled high CO2 solubility and facilitated formation of foams of high bubble density and small bubble size. The effects of foaming temperature, foaming time and CNTs concentration on the foam expansion ratio was investigated. The morphology of the prepared foams was studied by SEM. The compressive properties of the foams were measured and toughness determined. The nanocomposite foams with 0.5% CNT show improvement in energy absorbing capabilities. Upon further increasing CNT concentration, the capability decreases. Further analysis revealed that this was due to the non-uniform foam morphology in those nanocomposite foams. This in turn resulted in from the mixed nucleation mechanisms because of the insufficient CNT dispersion when foamed from the retrograde phase. Enhancement of CNT dispersion in the matrix is needed in order to improve the uniformity of the foams and realize the potential of these materials.
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Date Issued: 2011
Identifier: FSU_migr_etd-3037
Format: Thesis

Title: Theoretical and Experimental Investigation of Buckypaper: Field Emission.
Creator: Chen, Yiwen, Wang, Ben, Zhang, Mei, Brooks, James S., Liang, Richard, Zhang, Chuck, Vanli, O. Arda, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Many researchers regard carbon nanotube backlight units (CNT-BLUs) as a potential candidate for the liquid crystal display (LCD) industry. CNT buckypapers were tested as surface luminary sources for CNT-BLU applications. The field emission properties, durability and repeatability of a single-walled Carbon nanotube (SWCNT) buckypaper was studied for developing CNT-BLU. This study reports a laser irradiation process to enhance the field emission properties of buckypaper, which is a thin sheet...
Show moreMany researchers regard carbon nanotube backlight units (CNT-BLUs) as a potential candidate for the liquid crystal display (LCD) industry. CNT buckypapers were tested as surface luminary sources for CNT-BLU applications. The field emission properties, durability and repeatability of a single-walled Carbon nanotube (SWCNT) buckypaper was studied for developing CNT-BLU. This study reports a laser irradiation process to enhance the field emission properties of buckypaper, which is a thin sheet of high-loading carbon nanotube networks. A scanning laser treated selected regions of the buckypaper to activate CNT emitters. This post-process causes a decrease in turn-on field and increases in the field enhancement factor ( and #946;), luminance intensity and uniformity of buckypaper emitters. The phosphorescence luminance intensity and uniformity of buckypaper emitters were measured and characterized. These exellent properties and performance were achieved by adjusting machining parameters of laser power, laser lens motion speed, laser resolution. Design of Experiment (DOE) methodology provided a method to rapidly search the feasible laser parameter setting for processing buckypaper and improving field emission properties within fewer experimental runs. DOE results indicated the proper laser treatment power density was 0.9 W/cm2. Furthermore, the effects of the laser treated emitter density was investigated under the same laser power density as the DOE results. The CNT emitter's altitude, diameter and spacing were characterized through an optics analysis after laser treatment. The emitter spacing directly impacted emission results when the laser power and treatment time were fixed. The increasing emitter density gave rise to an enhanced field emission current and luminance. However, a continuous and excessive increase of emitter density with spacing reduction generated a screening effect. As a result, the extended screening effect from the smaller spacing eventually crippled the field emission effectiveness. From luminance intensity and uniformity of field emission, the optimal ratio of average emitter altitude to emitter spacing was 3.4. The high effective buckypaper is suggested to have a density of 50 50 emitters/cm2, which presents an effective field enhancement factor of 3721 and a moderated screening effect of 0.005. Proper laser treatment appears to be an effective post-treatment process for optimizing field emission and luminance performance for a buckypaper cold cathode.
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Date Issued: 2010
Identifier: FSU_migr_etd-7113
Format: Thesis

Title: Nanostructure-Based Modeling and Experimental Characterization of Electrical Conductivity of Carbon Nanotube Networks.
Creator: Li, Shu, Liang, Richard, Andrei, Petru, Wang, Ben, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Carbon nanotubes (CNTs) possess exceptional electrical properties. Networks of densely packed nanotubes that are formed by intercontacted or interconnected nanotubes and bundles were observed to form electrically conducting pathways over macroscopic dimensions and can be used for fabricating electronic devices and multifunctional composites. However, the electrical conductivity of these macroscopic networks is much less than the individual CNT's performance, primarily due to the large contact...
Show moreCarbon nanotubes (CNTs) possess exceptional electrical properties. Networks of densely packed nanotubes that are formed by intercontacted or interconnected nanotubes and bundles were observed to form electrically conducting pathways over macroscopic dimensions and can be used for fabricating electronic devices and multifunctional composites. However, the electrical conductivity of these macroscopic networks is much less than the individual CNT's performance, primarily due to the large contact resistance between nanotubes. Many factors contribute to the contact resistance, and the majority of these factors are difficult to directly measure and control due to nanoscale dimensions. The approach of physics-based simulation would help to understand the dominating factors of carbon nanotube networks (CNNs) conductivity. In this thesis work, experimental characterization of the nanostructures and electrical properties of CNNs were carried out, and an equivalent electrical circuit model of CNNs was improved to study the electrical conduction mechanism and properties. To systematically investigate the structure-property relationship between the conductivity of CNNs and their nanostructures, microscopic images of CNNs were characterized with image analysis software to obtain the CNT rope length and diameter distributions. Volume fractions of CNTs in these CNNs were also determined by experimental measurements and literature reported density of CNTs. Raman spectroscopy results were used to characterize the alignment degree of magnetically aligned CNNs. The electrical properties of CNNs, including electrical conductivity and current-carrying capacity tests, were carried out. The conductivities of various types of CNNs were obtained, including single-walled nanotubes (SWNTs), multi-walled nanotubes (MWNTs), and carbon nanofibers (CNF). CNNs of pure SWNTs possess the highest conductivity among all the networks studied. Another important electrical property, the current-carrying capacity, was also studied to understand the breakdown mechanism of CNNs. The tests were conducted to characterize the breakdown temperature and current density of the CNNs. It was determined that the breakdown of CNNs under high current stimuli was due to Joule heating. The modified electrical conductivity model is an electrical circuit simulation approach that reflects multiscale electrical conduction mechanisms and statistical nature of the CNNs. The model begins with nanoscale factors such as nanotube chirality and contact type, and then incorporates microscale factors such as dispersion and nanotube orientation, and further uses circuit computation simulation to calculate the bulk conductivity of the CNNs. Case studies were conducted to first validate the model and then reveal the structure-property relationships of different types of CNNs, including the effects of CNT orientation and chirality on the conductivity of the CNNs. The experimental results and developed model can be used to design and optimize CNNs for electrical applications.
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Date Issued: 2009
Identifier: FSU_migr_etd-7182
Format: Thesis

Title: Thermal Management Composites Utilizing Carbon Nanotubes and High-Conducting Carbon Fibers: Design, Fabrication and Characterization.
Creator: Zimmer, Michael Makoto, Liang, Zhiyong Richard, Wang, Ben, Brooks, James, Zhang, Chun (Chuck), Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: The focus of the dissertation is to find solutions to increase the through-thickness thermal conductivity of fiber-reinforced polymer matrix composites (PMC). The objective is to explore novel concepts and new approaches to improve the through-thickness thermal conductivity up to 30W/mK for PMCs. First, this research involves understanding the principles of thermal transport in composite and nanocomposite materials. Then the research proceeds to model and design high thermal conducting...
Show moreThe focus of the dissertation is to find solutions to increase the through-thickness thermal conductivity of fiber-reinforced polymer matrix composites (PMC). The objective is to explore novel concepts and new approaches to improve the through-thickness thermal conductivity up to 30W/mK for PMCs. First, this research involves understanding the principles of thermal transport in composite and nanocomposite materials. Then the research proceeds to model and design high thermal conducting composites and develop fabrication processes and characterization methods for functioning prototype materials. PMCs are advantageous for their light-weight, excellent strength and high modulus properties. However, due to insulation nature of polymer resin matrices, their bulk composites demonstrate poor through-thickness thermal conductivity making it unsuitable for applications that undergo thermal loads requiring a means for adequate heat dissipation. The research has carried out four technical approaches to achieve high through-thickness thermal conductivity. 1. Conductive Resins: Increasing the thermal conductivity of the matrix would increase the bulk through-thickness thermal conductivity. Experiments have been done using conductive fillers such as metallic nanoparticles and carbon nanotubes. Results have shown increase in the thermal conductivity but with the disadvantage of increased matrix viscosity making the fabrication process difficult. The thermal conductivity increases, however, is not adequate to achieve the objective solely. 2. Stitch Method: This method applies a continuous conductive path by stitching or inserting high conducting materials such as metal wires, high conducting carbon fiber or high conducting carbon yarns in the through-thickness direction of the composites. Experimentally, this method has proven to show a 27 fold increase in the through-thickness thermal conductivity at low volume fraction percentage of 5% with copper wire and 3.5 fold increase using K-1100 carbon yarn. 3. Long MWNT: Long MWNTs should create a conductive microstructure between fiber layers in composites. Providing conductive links improve the thermal transport of phonons, long MWNTs should more effectively provide thermal transport between fiber layers. However, the experimental results have yet to yield any improvements in the thermal properties of the composites. 4. Buckypaper: The use of thin film of dense nanotube networks or buckypapers is to improve the thermal connections between fiber layers as an interlayer material. If the buckypaper can make multiple connections between fiber layers, the nanotube network can be used to facilitate thermal transportation. However, the use of buckypaper has shown to have a reduced thermal conductivity value than that of a composite without buckypaper. Buckypaper in the experiment create resin rich areas between layers. Modeling efforts were performed to understand thermal transport mechanism, find solutions and predictions to through-thickness thermal conductivity of the multiscale composites. Micromechanical models were used to predict thermal property values for conductive resins as well as nanoparticle/fiber multiscale composites. Results show that only a few models prove useful with close predictions to experimental data. On the other hand, finite element modeling (FEM), allows the exploration of the critical nanoparticle/fiber interactions and their effects on thermal properties of the resultant composites. The FEM results show that it is the interconnections between nanoparticle and fibers, rather than concentration of conductive fillers, significantly impact the through-thickness thermal conductivity in PMCs, where continuous thermal pathways were the most important for performance improvement. Discontinuous pathways of nanotubes and conducting materials showed very limited or no effects on thermal conductivity improvements. These results provide viable information for future design and fabrication of high through-thickness thermal conductivity composite materials for thermal management multifunctional applications.
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Date Issued: 2009
Identifier: FSU_migr_etd-7265
Format: Thesis

Title: Assessment of Response Surface Modeling Techniques for Parametric Analyses of Computationally Expensive Simulations.
Creator: Martin, Aaron R., Pignatiello, Joseph J., Vanli, Arda, Baldwin, Thomas, Steurer, Mischa, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Traditional experimental design techniques have long been employed in industrial, agricultural, and other physical settings to characterize and optimize systems and processes. Such physical systems are characterized by random error, resulting in inconsistent behavior under identical operating conditions. The issues associated with such a random error (or stochastic) component have been addressed in classical design of experiments (DOE), and methods for handling such error are well documented...
Show moreTraditional experimental design techniques have long been employed in industrial, agricultural, and other physical settings to characterize and optimize systems and processes. Such physical systems are characterized by random error, resulting in inconsistent behavior under identical operating conditions. The issues associated with such a random error (or stochastic) component have been addressed in classical design of experiments (DOE), and methods for handling such error are well documented by Myers (2002). In many modern applications, adequate experimentation of physical systems is too costly and/or time consuming, so Fang et al. (2006) suggest that computer simulations are becoming more prominent as computing power increases. Simulations serve as surrogates of physical systems and make use of uncertain or imprecise parameters. Insight about a physical system derived from a simulation should be taken into account with this uncertainty. Sensitivity and uncertainty analyses are tools that support validation and verification and allow an experimenter to place confidence in simulation results. One means to satisfy this end is by conducting and analyzing a computer experiment. A computer experiment is defined by Currin (1988) as a collection of runs from a simulation in which a record of response variables are logged and examined. Many computer simulations are deterministic, that is identical operating conditions produce no variability in system performance. This poses a problem for traditional statistical modeling methods that are related to DOE, as these classical methods assume that the errors are independently and identically distributed. Models derived from ordinary least squares (OLS) regression assume that variance is fixed over the design space. However, Fang et al. (2006) mention that a deterministic simulation does not have constant variance, as observed points in the design space are precisely known. Because usual uncertainty measurements derived from OLS residuals are not sensible in this case, Currin (1988), Denison et al. (2002), Fang et al. (2006), and Sacks (1989) suggest that a Bayesian approach to regression modeling is more appropriate than traditional techniques because traditional, non-Bayesian approaches fail to take uncertainty of the parameters into account. Bayesian methods involve optimization over the unknown parameters and allow the modeler to make prior assumptions on the regression variance and therefore may be better suited for predicting unobserved responses. The following study compares traditional methods to other techniques including Bayesian regression.
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Date Issued: 2009
Identifier: FSU_migr_etd-2700
Format: Thesis

Title: Assessment of Triboluminescent Materials for Intrinsic Health Monitoring of Composite Damage.
Creator: Dickens, Tarik J., Okoli, Okenwa, Dalal, Naresh, Liu, Ted, Liang, Richard, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Advanced composites offer robust mechanical properties and are widely used for structural applications in the aerospace, marine, defense and transportation industries. However, the inhomogenous nature of composite materials leaves them susceptible to problematic failure; thus the development of a means for detecting failure is imperative. Damage occurs when a load is applied and a distortion of the solid material results in deformation. This process also results in straining of the material....
Show moreAdvanced composites offer robust mechanical properties and are widely used for structural applications in the aerospace, marine, defense and transportation industries. However, the inhomogenous nature of composite materials leaves them susceptible to problematic failure; thus the development of a means for detecting failure is imperative. Damage occurs when a load is applied and a distortion of the solid material results in deformation. This process also results in straining of the material. Strain, however, is a physical result of work being performed on a solid material making energy the commonality among all failure mechanisms. This study investigated the feasibility of using Triboluminescent zinc-sulphide manganese (ZnS:Mn) phosphors concentrated in vinyl ester resin for damage monitoring of polymer composites under flexural loading. These particulates react to straining or fracturing by emitting light of varied luminous intensity and detecting the crack initiation presently leading to catastrophic failure(s). Unreinforced vinyl ester resins and fiber-reinforced composite beams incorporated 5 - 50 % wt. concentrations of TL fillers, and were subjected to three-point bend tests. The intent of flexural testing was to observe the transient response of triboluminescence (TL) in both two- and three-phase composite systems throughout the failure cycle of notched beams, while changing the geometric constraints. Results indicate TL crystals emit light at various intensities corresponding to crystal concentration, the notch-length and imminent matrix fracture. The fracturing or deformation energy was estimated by the method of J-integral with varied notch-lengths, where a lower threshold for excitation was found to be approximately <2 J/m^2, far below its critical fracture energy (~ 3 & 7 J/m^2). Consequently, concentrated samples showed nearly 50 % reductions of mechanical moduli due to high loading levels, which subsequently affected the Triboluminescent response. As a result, an optimal 6 % vol. of TL particulates was chosen for further study and exhibited significant signal-to-noise response. Scanning electron microscopy (SEM) revealed particulate inclusions with shearing bands and semblance of particle to resin adhesion, as well as, cases of micro-cracking in reinforced samples. Despite significant parasitic affect to mechanical properties, the luminescent properties of TL occur at rupture for unreinforced composites. The cases of TL concentrated reinforced composites show detection of localized matrix phenomenon which are related to the material response and incurring internal strain-energy prior to any catastrophic failure. This indicates that TL in composite systems has the potential to detect micro-failures (micro-cracks) related to the weak matrix component. The triboluminescent signal was simulated as a rate-dependent model considering the load profile of the composite beam is known.
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Date Issued: 2013
Identifier: FSU_migr_etd-7772
Format: Thesis

Title: Multiple Criteria Third-Order Response Surface Design and Comparison.
Creator: Yang, Ying, Pignatiello, Joseph J., Awoniyi, Samuel., Vanli, Arda, Okoli, Okenwa, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: This research focuses on the third-order response surface designs for global optimization and mapping of systems or processes. The current second-order response surface designs may not be accurate and efficient enough to describe the true model of the systems or processes in terms of multiple design criteria. This research addresses the needs for third-order designs by identifying corresponding inaccuracy issues and attempts to create efficient designs by investigating different ways of...
Show moreThis research focuses on the third-order response surface designs for global optimization and mapping of systems or processes. The current second-order response surface designs may not be accurate and efficient enough to describe the true model of the systems or processes in terms of multiple design criteria. This research addresses the needs for third-order designs by identifying corresponding inaccuracy issues and attempts to create efficient designs by investigating different ways of building third-order models. This research proposes functionality as a new design property to guide the comparison of practicability and ease of use of different designs. Furthermore, it looks into generating multiple criteria optimal third-order designs for continuous cuboidal region using NSGA-II algorithm. IV-optimality and space filling have been selected as the two primary objectives for this multiple criteria third-order design problem. This research shows that the NSGA-II does not provide the results as expected for third-order designs, and nested faced centered design is the best overall design in IV-optimality, space filling, orthogonality and functionality. A Pareto-optimal front is given to satisfy different practitioners' needs.
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Date Issued: 2008
Identifier: FSU_migr_etd-1062
Format: Thesis

Title: A Study of Nanostructure and Properties of Mixed Nanotube Buckypaper Materials: Fabrication, Process Modeling Characterization, and Property Modeling.
Creator: Yeh, Cherng-Shii, Liang, Zhiyong, Zheng, Jim P., Wang, Ben, Zhang, Chuck, Jack, David, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Single-walled carbon nanotube buckypaper (SBP) is a thin film of preformed nanotube networks that possesses many excellent properties. SBP is considered to be very promising in the development of high-performance composite materials; however, the high cost of single-walled nanotubes (SWNTs) limits industrial applications of SBP materials. Mixed buckypaper (MBP) is a more affordable alternative that combines SWNTs with low-cost multi-walled nanotubes (MWNTs) or carbon nanofibers (CNFs) to...
Show moreSingle-walled carbon nanotube buckypaper (SBP) is a thin film of preformed nanotube networks that possesses many excellent properties. SBP is considered to be very promising in the development of high-performance composite materials; however, the high cost of single-walled nanotubes (SWNTs) limits industrial applications of SBP materials. Mixed buckypaper (MBP) is a more affordable alternative that combines SWNTs with low-cost multi-walled nanotubes (MWNTs) or carbon nanofibers (CNFs) to retain most of the excellent properties of SBP while significantly reducing the cost. This study proposes a manufacturing process of MBPs. The process parameters were studied through experimental design and statistical analysis. The parameters included mixing material type, mixing ratio, sonication effect, surfactant amount, and cleaning effect. The effects of the parameters on nanostructure uniformity, purity, Brunauer-Emmett-Teller (BET) surface area and electrical conductivity of the resultant MBPs were revealed. Results of the study show that all those parameters and their interactions are influential to the dispersion and uniformity of nanostructure and purity, but only mixing material type and ratio are influential to the BET surface area and electrical conductivity. To systematically reveal the process-nanostructure-property relationship of SBP and MBP materials, the nanostructures of the buckypapers were characterized as rope size, length and pore size distributions of the nanomaterials in resultant buckypapers. These distributions featured bimodal phenomenon due to different material mixtures; therefore, the distributions were further separated into two individual ones and fitted into Weibull distributions. Two nanostructure-property models of buckypaper materials were developed. The specific surface area model was built upon the characterization and analysis of buckypaper nanostructures. The model showed that rope size distribution and mixed ratio of nanomaterials are governing factors for the resultant specific surface area of buckypaper. The electrical conductivity model captured multiscale electrical transport phenomenon of nanotube networks in buckypapers. The model considered chirality, contact area, contact type, diameter, length and orientation distributions of nanotubes in buckypapers. The proposed models not only can predict property trends correctly, but can also reveal the critical process-nanostructure-property relationships of buckypaper materials. The results are important for the further tailoring and optimization of the manufacturing process and properties of nanotube buckypapers.
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Date Issued: 2007
Identifier: FSU_migr_etd-0947
Format: Thesis

Title: Nanotube Buckypaper Electrodes for PEM Fuel Cell Applications.
Creator: Ku, Chung-Lin, Liang, Zhiyong, Zheng, Jim P., Wang, Ben, Zhang, Chuck, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Many researchers proposed the use of carbon nanotubes as an advanced metal catalyst support for electrocatalysis applications. In this research, buckypaper (thin film of preformed nanotube network) electrodes with different weight ratios of carbon nanomaterials, including SWNT, MWNT, CNF, and Vulcan XC-72 (CB), were fabricated and compared by their electrochemical properties using cyclic voltammetry (CV) test. Platinum (Pt) nanoparticles were successfully electrodeposited on the mixed...
Show moreMany researchers proposed the use of carbon nanotubes as an advanced metal catalyst support for electrocatalysis applications. In this research, buckypaper (thin film of preformed nanotube network) electrodes with different weight ratios of carbon nanomaterials, including SWNT, MWNT, CNF, and Vulcan XC-72 (CB), were fabricated and compared by their electrochemical properties using cyclic voltammetry (CV) test. Platinum (Pt) nanoparticles were successfully electrodeposited on the mixed buckypapers in mixed ethylene glycol, H2PtCl6, and H2SO4 aqueous solutions by applying a potential pulse at 0.2 and -0.25 V, forming Pt/mixed buckypaper electrodes. The dispersion and particle size of Pt nanoparticles on the buckypapers were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The average diameter of Pt nanoparticles on the buckypapers was 10 nm. Surface areas of the Pt nanoparticles on the mixed buckypapers were determined by cyclic voltammogram measurements in 0.5 M H2SO4 solution, and electrocatalytic performances of the resultant buckypaper electrodes were observed. Compared to the Pt/CB electrodes, the Pt/SWNT+MWNT buckypaper electrode exhibits higher electrocatalytic performance. The highest electrochemical surface area (ECSA) of Pt/SWNT+MWNT (1:3) electrodes reaches 43.7m2/g and is about 1.6 times higher than that of the Pt/CB electrode. This may be attributed to the small particle size and good dispersion of platinum, high conducting property of carbon nanotubes, special deposition phenomenon, and unique three–dimension electrode structure. The research results suggest that mixed buckypapers are good candidates for catalyst supports in fuel cell applications because of their high electrocatalytic performance. The reduction of the amount of precious metal catalyst (Pt) needed is important for real-world applications. Further research into the optimization of Pt deposition and nanostructure of mixed buckypapers could lead to highly efficient and potentially affordable electrodes for fuel cell applications.
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Date Issued: 2007
Identifier: FSU_migr_etd-2959
Format: Thesis

Title: Finite Element Modeling of a Transit Bus.
Creator: Nimbalkar, Ravindrakumar, Okoli, Okenwa, Wekezer, Jerry, Braswell, Robert, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Most of the Federal Motor Vehicle Safety Standards applicable to school buses do not specifically cover the cutaway type of buses assembled on ladder-type chassis, for which a production process is split into two stages. In the first stage, the chassis and cab section are assembled by automobile manufacturers. In the second stage, the vehicle is shipped to another company where the bus body and additional equipment are installed. Lack of strict structural standards for transit bus body...
Show moreMost of the Federal Motor Vehicle Safety Standards applicable to school buses do not specifically cover the cutaway type of buses assembled on ladder-type chassis, for which a production process is split into two stages. In the first stage, the chassis and cab section are assembled by automobile manufacturers. In the second stage, the vehicle is shipped to another company where the bus body and additional equipment are installed. Lack of strict structural standards for transit bus body builders necessitates the crashworthiness and safety evaluation of this category of vehicles. Such an assessment process is imperative since these transit buses are often used to transport disabled passengers. A full scale crash test is considered the most reliable source of information regarding structural integrity and safety of motor vehicles. However, the high cost of such tests and difficulties in collecting data results in an increasing interest in the analytical and computational methods of evaluation. Theses methods allow for extensive safety studies once the finite element model is validated. A reliable analytical investigation can reduce the cost dramatically and allow faster introduction of the new solutions. This thesis research work presents the procedure for development of a finite element (FE) model of a public transit bus and the results of its crashworthiness and structural integrity analysis. The finite element model was developed based on the geometry obtained by disassembling and digitizing all major parts of the actual bus. The FE model consists of 73,600 finite elements, has 174 defined property sets (groups of elements with the same features) and 23 material models. All parts are connected using different multi point constraints and special links with failure to model actual types of structural connections such as bolts and spot welds. LS-DYNA non-linear, explicit, 3-D, dynamic FE computer code was used to simulate behavior of the transit bus under different impact scenarios, such as frontal impact and side impact at various velocities.
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Date Issued: 2003
Identifier: FSU_migr_etd-2589
Format: Thesis

Title: Generalized Cumulative Sum Control Charts.
Creator: McCulloh, Ian, Pignatiello, Joseph J., Okoli, Okenwa I., Simpson, James R., Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Industrial manufacturing processes can experience a variety of changes to important quality characteristics as a result of tool breakage, tool wear, introduction of new raw materials, and other factors. Statistical process control charts are often used to monitor for changes in quality characteristics for manufacturing processes. The control chart computes a statistic based on measured observations of the process and compares it to control limits. When the statistic exceeds a control limit,...
Show moreIndustrial manufacturing processes can experience a variety of changes to important quality characteristics as a result of tool breakage, tool wear, introduction of new raw materials, and other factors. Statistical process control charts are often used to monitor for changes in quality characteristics for manufacturing processes. The control chart computes a statistic based on measured observations of the process and compares it to control limits. When the statistic exceeds a control limit, the control chart signals that the process is out-of-control. Quality engineers would then search for the special cause responsible for the change in the process. Rapid detection by the control chart is important to minimize the production of poor quality items as a result of an out-of-control process. Control charts that detect changes rapidly can therefore save critical process down-time and expense. This research investigates several new control charts related to the commonly used cumulative sum (CUSUM) control chart. The new control charts use control limits that change as a function of the number of process observations instead of remaining constant. The performances of these new control charts are compared to several other charts including the Shewhart chart, the CUSUM, and the exponentially weighted moving average charts. Compared to the standard CUSUM, the proposed control charts can detect a change in a process more rapidly for a given range of shifts in the mean of a process. The proposed control charts offer a flexibility to quality engineers for better optimization of monitoring schemes for manufacturing processes.
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Date Issued: 2004
Identifier: FSU_migr_etd-2593
Format: Thesis

Title: Continuous Buckypaper Manufacturing Process: Process Investigation and Improvement.
Creator: Young, Jasmine, Liang, Zhiyong, Wang, Ben, Zhang, Chuck, Vanli, Arda, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Carbon nanotubes have excellent electrical, thermal, and mechanical properties as determined theoretically and experimentally. Their properties make them great candidates for use in a number of applications ranging from lightning strike protection for airplanes to computer heat sink. However, carbon nanotubes are incredibly small, with diameters as small as 1nm and just a few micrometers long. The nanoscale size makes carbon nanotubes impractical to be used individually for many industrial...
Show moreCarbon nanotubes have excellent electrical, thermal, and mechanical properties as determined theoretically and experimentally. Their properties make them great candidates for use in a number of applications ranging from lightning strike protection for airplanes to computer heat sink. However, carbon nanotubes are incredibly small, with diameters as small as 1nm and just a few micrometers long. The nanoscale size makes carbon nanotubes impractical to be used individually for many industrial purposes, thus methods have been developed to fabricate macroscale networks of carbon nanotubes. The carbon nanotube networks, also called Buckypaper, have showed mechanical, thermal and electrical properties inferior to those of individual nanotubes. Extensive work has been conducted to develop and optimize suitable production methods of producing high quality Buckypaper and enhance their properties. Many approaches are capable of producing a carbon nanotube network, but most are not able to scale up for industrial applications due to size and production rate limitations. This research focuses on two aspects of Buckypaper manufacturing improvements. The first is to test 90 mm samples of Buckypaper disks to determine the impact of each processing parameter on the quality and properties. Statistic analysis was used to reveal the effect of processing parameters. Utilizing these results, a long sample of Buckypaper was produced and examined for property and quality consistency along the sample length, using modified customer-made continuous filter devices. Additionally, long samples with larger width were produced to demonstrate production rate of continuous Buckypaper manufacturing. Through this research it was found that the electrical conductivity of the Buckypaper was affected positively by an increase in sonication pressure. Additionally, increases in pressure and increase in power of sonication led to an increase of Buckypaper strength. Strength and electrical properties of the continuous Buckypaper were considered consistent throughout the length. These results provide essential understanding of the continuous Buckypaper manufacturing process.
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Date Issued: 2009
Identifier: FSU_migr_etd-0872
Format: Thesis

Title: Development of Carbon Nanotube/Carbon Fiber Multiscale Reinforcement Composites.
Creator: Davey, Kirk-Duval S., Liang, Richard, Okoli, Okenwa, Sands, James, Parker, Reginald, Wang, Ben, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: High performance composites are currently being used in the marine, automotive, aerospace and defense industries. These industries demand materials with properties that are similar or better than conventional metals at a fraction of the weight. The development of nanoparticle reinforced composites is presently one of the most explored areas in materials science and engineering. The exceptional properties of nanoparticles have made them a focus of widespread research. By combining...
Show moreHigh performance composites are currently being used in the marine, automotive, aerospace and defense industries. These industries demand materials with properties that are similar or better than conventional metals at a fraction of the weight. The development of nanoparticle reinforced composites is presently one of the most explored areas in materials science and engineering. The exceptional properties of nanoparticles have made them a focus of widespread research. By combining nanoparticles with traditional reinforcement materials, multiscale composites can be produced with superior properties to that of regular composites. This research focuses on the development of multiscale reinforcement composites, through the use of carbon nanotubes (CNTs), IM7 and T800 carbon fibers and SC-79 epoxy resin. Vacuum assisted resin transfer molding and hand lay-up/ vacuum bagging processes were evaluated for the manufacturing of multiscale composites. Results from this research showed that the use of carbon nanotubes can increase the tensile strength by up to 27% and toughness by up to 38%, with the addition of 2.5wt% multiwall carbon nanotubes (MWNTs). However there were no significant changes in the flexural properties with the addition of carbon nanotubes. Analysis of the fracture surfaces, using scanning electron microscopy showed that there was good dispersion of the carbon nanotubes through out the matrix material. The good dispersion of tubes aided in toughening the SC-79 epoxy resin. This toughening effect was evident though the change in crack propagation patterns on the fracture surface. There was also evidence of the nanotubes bridging cracks and holding resin particles together, which also lead to increased fracture toughness
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Date Issued: 2005
Identifier: FSU_migr_etd-0823
Format: Thesis

Title: Polypyrrole as a Smart Material for Phosphate Contaminate Detection in Water.
Creator: Woodard, Yoshino N., Owusu, Yaw A., Parker, Reginald, Kalu, Peter N., Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Polypyrrole is a conductive polymer that has the potential to be used in many systems where conductivity can be studied. Polypyrrole when combined with a catalyst such as calcium acetate maybe able to provide a method of detecting phosphate in water systems. The hypothesis of this research explores the concept that a polypyrrole sensor could be manufactured via a casting method to produce a sensor that detects phosphates in water. Varying three primary factors produced a designed experiment...
Show morePolypyrrole is a conductive polymer that has the potential to be used in many systems where conductivity can be studied. Polypyrrole when combined with a catalyst such as calcium acetate maybe able to provide a method of detecting phosphate in water systems. The hypothesis of this research explores the concept that a polypyrrole sensor could be manufactured via a casting method to produce a sensor that detects phosphates in water. Varying three primary factors produced a designed experiment and ANOVA analysis and comparison of means for three response variables: voltage, resistance and conductivity (calculated). Careful attention was paid to the values of the response variables across the geometry of the sensor prototypes. The sensor was evaluated for accuracy, sensitivity after multiple uses, and selectivity. After examining all of the data, the information obtained did not disprove the hypothesis, however it pointed to calcium acetate as the most powerful factor in the polypyrrole sensor in the accuracy test. Sensitivity and Selectivity tests had mixed findings. The samples not containing calcium acetate near the surface did not produce great changes in the response variables. The work presented in this thesis is an analysis of the raw data and materials used for generating the polypyrrole sensor prototype in order to introduce a new concept for manufacturing sensors using advanced materials; namely smart structures as sensors.
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Date Issued: 2006
Identifier: FSU_migr_etd-0787
Format: Thesis

Title: Design, Installation, and Solar Energy Efficiency Assessment Using a Dual‐Axis Tracker by.
Creator: Wang, Kaifan Kyle, Owusu, Yaw A., Awoniyi, Samuel A., Kalu, Egwu E., Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Environmental and economic problems caused by over-dependence on fossil fuels have increased the demand and request for green energy produced by alternative renewable sources. Producing electricity by using photovoltaic cells (also called solar cells) is a fast growing industry. There are two main ways to make photovoltaic cells more efficient. One method is to improve the materials design and the other is to optimize the output by installing the solar panels on a tracking base that follows...
Show moreEnvironmental and economic problems caused by over-dependence on fossil fuels have increased the demand and request for green energy produced by alternative renewable sources. Producing electricity by using photovoltaic cells (also called solar cells) is a fast growing industry. There are two main ways to make photovoltaic cells more efficient. One method is to improve the materials design and the other is to optimize the output by installing the solar panels on a tracking base that follows the sun. This research employed the latter method. The main purpose of the thesis was to design and assemble of a dual-axis solar tracker with a view to assess the improvement in solar conversion efficiency. A comparative analysis was performed using three systems, i.e., Dual-Axis Tracking, Single-Axis Tracking and Stationary Modules. ¡®¡¯Design Expert 6.0¡± statistical software was used to process the design of experiment and to determine the effects of four chosen factors (Tracking or No Tracking, Type of Modules, Time of the Day, and Weather Condition). The results showed that the use of the Dual-Axis Tracking System produced 18% gain of power output, compared with a Single-Axis Tracking System. The gain of output power with the Dual-Axis Tracking System was much higher (53%) when compared with a stationary system inclined at 30¢ª to the horizontal. A benefit-cost analysis performed on the three systems showed that the unit cost of energy produced by the Dual-Axis Tracker is $0.53, which is reasonable, considering the state of the technology and the potential added benefit of any future amortization when employed on a large scale.
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Date Issued: 2008
Identifier: FSU_migr_etd-1262
Format: Thesis

Title: Investigation and Development of the Resin Infusion Between Double Flexible Tooling (RIDFT) Process for Composite Fabrication.
Creator: Thagard, James Robert, Liang, Zhiyong, Chen, Ching-Jen, Wang, Ben, Zhang, Chuck, Simpson, James, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: This research presents a study on an innovative composite manufacturing process called Resin Infusion between Double Flexible Tooling (RIDFT). In this process, resin is infused between two flexible tools through fiber reinforcements in a two-dimensional flat shape. The wetted reinforcements and flexible tooling are then formed over a mold into a specified part shape by use of vacuum. The RIDFT process has potentials for rapidly and affordably producing large composite parts. This research...
Show moreThis research presents a study on an innovative composite manufacturing process called Resin Infusion between Double Flexible Tooling (RIDFT). In this process, resin is infused between two flexible tools through fiber reinforcements in a two-dimensional flat shape. The wetted reinforcements and flexible tooling are then formed over a mold into a specified part shape by use of vacuum. The RIDFT process has potentials for rapidly and affordably producing large composite parts. This research details the development of the industrial RIDFT machine from its design to its fabrication and to the demonstration of its use. This new machine uses new techniques, integrating vacuum sealing, dynamic supporting and temporary resin distribution channels to achieve industrial application requirements. A design of experiment (DOE) approach is used to perform testing and analysis to validate the ability of the RIDFT process to form various geometries and identify limitations in formability and issues with wrinkling. Four specific fiber textile structures were studied in their ability to form over a half sphere of varying radii and a rectangular mold of varying corner radii. The number of fiber layers was also studied to understand the effects on forming. Fiber textile structure and fiber layers were shown to be significant for their influence on formability and wrinkling. To better understand the forming mechanics within the RIDFT process and to predict the formability of a desired geometry, a simulation model was required. The PAMFORM software was chosen for modeling because it is a general-purpose finite element package for the industrial virtual manufacturing of non-metallic sheet forming. PAMFORM is unique in its ability to model a variety of forming processes. This research details the development of the simulation model for the RIDFT process based on PAMFORM and describes the validation of the model through experimental methods. This development includes the modeling of multiple layers of resin-wetted reinforcements, silicone diaphragms and part geometries, as well as the modeling of contact interfaces and forming pressures. The systematic investigation has been done for characterizing fabric drapability, rubber deformation and friction interactions for developing the simulation model. The model results are then compared against experimental results for model validation. This validated model will allow the ability to predict drapability and fiber deformation during the process forming. The results of the simulation reveal mechanisms and influence factors of the drapability and wrinkling of the RIDFT process.
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Date Issued: 2003
Identifier: FSU_migr_etd-1611
Format: Thesis

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