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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: Development of Continuous Manufacturing Process for Magnetically Aligned and Random Nanotube Buckypaper.
Creator: Ugarte, Johnnattan, Liang, Richard, Wang, Ben, Zhang, Chuck, Park, Young-Bin, Brooks, James, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Fiber-reinforced composites are becoming more popular due to their high strength to weight ratio, making them a suitable replacement for traditional metals for lightweight applications. However, for applications where electro-conductivity and thermo-conductivity are required, fiber-reinforced composites lack the necessary properties without adding parasitic components. As a result of extensive research, high performance carbon nanotube-reinforced composites are considered as one of the key...
Show moreFiber-reinforced composites are becoming more popular due to their high strength to weight ratio, making them a suitable replacement for traditional metals for lightweight applications. However, for applications where electro-conductivity and thermo-conductivity are required, fiber-reinforced composites lack the necessary properties without adding parasitic components. As a result of extensive research, high performance carbon nanotube-reinforced composites are considered as one of the key solutions to this issue, with buckypapers serving as the central constituent. Buckypapers are thin membranes of well-dispersed networks of nanotubes held together by van der Waals forces. Buckypapers are considered as one of the promising candidates for incorporating nanotubes into composite manufacturing due to their ease of handling and the ability to transfer the properties of the nanotubes into the resultant composites. Buckypapers enable thermal and electro-conductivity in ranges not possible using fiber composites alone. The objective of this research is to develop an effective, affordable manufacturing process capable of continuously fabricating buckypaper materials to meet market demands, as well as property and quality requirements from the consumers. The batch method of buckypaper manufacturing processes have been investigated and standardized by previous studies. Successful results under the standardized process have been adopted to pilot buckypaper production. Such studies have also attracted the interest of industrial consumers who require large-scale manufacturing, and continuity of buckypaper materials, which are not offered by the current batch method. Through the development of four generations of prototypes, this research has successfully designed and fabricated the Nano Material Continual Integration System (NM-CIS), a filtration system capable of producing high quality continuous buckypaper materials. A prototype to produce continuous 1.5in wide buckypapers of randomly-dispersed SWNTs has been successfully developed. Furthermore, the research has characterized the physical and electrical properties and compared them with current batch-production buckypapers. The results indicate that the continuous manufacturing processes have the potential to scale-up production of continuous buckypaper products to achieve desired quality, continuity and affordability for potential industrial applications. Furthermore, the research has designed and fabricated the MA-CIS system to fabricate continuous magnetically aligned buckypaper materials, and the W-CIS system to produce 11-in wide-buckypaper
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Date Issued: 2007
Identifier: FSU_migr_etd-1466
Format: Thesis

Title: Development and Parametric Studies of Carbon Nanotube Dispersion Using Electrospraying.
Creator: Chen, Meei-Jiun, Zhang, Chuck, Park, Young-Bin, Liang, Zhiyong, Pignatiello, Joseph J., Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Since the discovery of carbon nanotubes in the early 1990s, a new era in nanotechnology opened up, impacting both scientific and technological fronts. One of the key challenges in processing of carbon nanotube-based materials and structures is proper dispersion of the nanoconstituents. Fundamental roadblocks to maximumize utilization of the exceptional properties of carbon nanotubes are their tendency to aggregate due to intermolecular forces and the resulting difficulties in dispersing them...
Show moreSince the discovery of carbon nanotubes in the early 1990s, a new era in nanotechnology opened up, impacting both scientific and technological fronts. One of the key challenges in processing of carbon nanotube-based materials and structures is proper dispersion of the nanoconstituents. Fundamental roadblocks to maximumize utilization of the exceptional properties of carbon nanotubes are their tendency to aggregate due to intermolecular forces and the resulting difficulties in dispersing them into individual tubes. In this study, a novel carbon nanotube dispersion technology that uses electrospraying was developed, analyzed, and evaluated. We established image analysis based measurement that can be used to quantify the degree and uniformity of carbon nanotube dispersion, and performed a series of designed experiments. Rigorous statistical analyses were conducted to investigate the parametric effect of electrospraying, and the design of experiments based models were derived. As validated through experiments, the design of experiments models can serve as effective guidelines for selecting the electrospraying parameters that allow controlled nanoparticle dispersion. Carbon nanotube electrospraying is expected to be applicable to a broad range of technical fields, owing to its low cost, ease of implementation, environmental friendliness, and scalability for industry use. Potential applications include, transparent, conductive carbon nanotube coating for flexible displays, multiscale carbon nanotube patterning, and continuous nanocomposite processing, the proofs-of-concept of which have been demonstrated in this study.
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Date Issued: 2007
Identifier: FSU_migr_etd-3849
Format: Thesis

Title: Development of Framework for Rapid Tool Manufacture for RIDFT Process.
Creator: Kuppusamy, Arvind, Zhang, Chuck, Okoli, Okenwa, Liang, Zhiyong, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Polymer composites are in a period of significant growth due to the increased use in the automobile, marine and aerospace application. Some of the advantages of using composites over other materials are weight savings, corrosion resistance and functional integration. However, long cycle times and higher tooling costs of the available manufacturing processes make it difficult to mass-produce composite products. Resin infusion double flexible tooling (RIDFT) is a novel process developed by the...
Show morePolymer composites are in a period of significant growth due to the increased use in the automobile, marine and aerospace application. Some of the advantages of using composites over other materials are weight savings, corrosion resistance and functional integration. However, long cycle times and higher tooling costs of the available manufacturing processes make it difficult to mass-produce composite products. Resin infusion double flexible tooling (RIDFT) is a novel process developed by the Florida Advanced Center for Composite Technologies (FAC2T) at FAMU-FSU College of Engineering aimed at tackling some of the above-mentioned problems. The use of one-sided mold provides a huge cost advantage over Resin Transfer Molding (RTM). However, using cost effective materials can reduce the cost further. In this thesis research, the various steps involved in the manufacture of the RIDFT mold were identified. The seven steps to manufacture a RIDFT mold are, Initial Graphics Exchange Standard (IGES) file tooling import/repair, mold design, material selection and preparation, NC programming, machine setup, machining and finishing and polishing. The problems at each of these stages were identified. The solutions to some of the problems, which might result in decrease in the tool manufacturing time, were found. To tackle with IGES file import problems some guidelines are presented. The various steps involved in the mold design stage are: compensation of permeable layer thickness, compensation of silicone layer thickness compensation of thickness of part and addition of draft surface. The tooling parameters compensation part of the mold design process was implemented by using both offset and scaling methods using C programming. The materials used for tooling until now are reviewed for pros and cons. Some of the tooling materials, that can be used in future, are also suggested. In order to help the mold manufacturer with the selection of machining parameters a macro was written in Microsoft Excel. Three cases were studied to show how the objectives of thesis are met.
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Date Issued: 2003
Identifier: FSU_migr_etd-3004
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: Design and Fabrication of Transparent Polycarbonate/Carbon Nanotube Composite Films.
Creator: Chin, Yuan-Chen (Craig), Park, Young-Bin, Wang, Ben, Liang, Zhiyong, Okoli, Okenwa, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Polycarbonate (PC) is a transparent, impact resistant polymer that provides protection against breakage or intrusion. The mechanical toughness of PC is reported to be associated with the molecular motion of main chain molecules. The molecular motion is present upon exposure to impact and can therefore provide efficient dissipation of impact energy. PC has found wide usages in military and commercial applications. This thesis investigates processing and characterization of transparent PC...
Show morePolycarbonate (PC) is a transparent, impact resistant polymer that provides protection against breakage or intrusion. The mechanical toughness of PC is reported to be associated with the molecular motion of main chain molecules. The molecular motion is present upon exposure to impact and can therefore provide efficient dissipation of impact energy. PC has found wide usages in military and commercial applications. This thesis investigates processing and characterization of transparent PC/carbon nanotube (CNT) composite films. The reinforcing capability and efficiency of CNTs in nanocomposites have been studied intensely world-wide due to their exceptional mechanical properties. Not only do they provide stiffness and strength, but they also have been reported to impart fracture toughness when dispersed in polymer matrices. As cracks develop in nanocomposites, CNTs serve as the bridging nanofibrils that effectively retard crack propagation. In some cases, CNTs act as obstacles that obstruct the crack propagation paths, thus increasing the energy needed to be dissipated for further crack opening. This research deals with two important issues in multi-walled carbon nanotube (MWNT)-based composites that are seemingly trade-offs – dispersion of high-loading MWNTs and maintenance of optical transparency. Higher loading of MWNTs is desired for increased reinforcing effects; however, it is limited by the difficulties in achieving uniform dispersion in the polymer resin due to increased viscosity and the tendency of MWNTs to aggregate. At the same time, only a small addition of MWNTs (less than 1 wt.%) makes the resin turn dark, which defeats the advantage of the transparency that should otherwise be retained by PC. PC/MWNT composite films (up to 0.15 wt.% MWNT) were fabricated using a solvent-based film casting method. Several optimization schemes were adopted to determine the most suitable solvent and the concentrations of PC/MWNT in the solvent. Solvent-induced PC crystallization, which was evidenced by milky tinting in the produced films, was minimized by identifying and optimizing the process parameters, namely, PC/MWNT/solvent solution viscosity, casting temperature, and film thickness. Design of experiments technique was used to determine the combination of optimal parameters.
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Date Issued: 2007
Identifier: FSU_migr_etd-3811
Format: Thesis

Title: Processing Technique and Mechanical Properties of Functionalized SWNT-Reinforced Composites.
Creator: Liao, Yu-Hsuan, Liang, Zhiyong, Wang, Ben, Zhang, Chuck, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Carbon nanotubes have exceptional mechanical and functional properties and are considered by many as the most promising reinforcement for the next generation high performance nanostructured materials. Tubes dispersion and interfacial bonding are the most critical issues for developing carbon nanotube-reinforced composites. Considerable improvements in the dispersion and interfacial bonding of single-walled carbon nanotube (SWNT)/ epoxy nanocomposites were obtained through developing new...
Show moreCarbon nanotubes have exceptional mechanical and functional properties and are considered by many as the most promising reinforcement for the next generation high performance nanostructured materials. Tubes dispersion and interfacial bonding are the most critical issues for developing carbon nanotube-reinforced composites. Considerable improvements in the dispersion and interfacial bonding of single-walled carbon nanotube (SWNT)/ epoxy nanocomposites were obtained through developing new fabricating techniques and functionalized SWNTs in this thesis research. By systematically investigating dispersion formulations, processing parameters, mechanical property tests and SEM observations, better tubes dispersion were achieved while dispersing nanotubes in a special dispersion system to form a stable solution and then mixing it with epoxy resin. Further functionalized nanotubes also improve the dispersion. Functionalization methods such as chopping, chopping-oxidizing, molecular wraping and directly oxidizing were used to create more active sites in the nanotubes for enhancing tube-resin interaction during processing and composite interface. Interfacial bonding improvement was studied through mechanical tests and SEM observations. The results shows that the storage modulus of nanocomposites is improved over the neat epoxy resin through better tubes dispersion, functionalized nanotubes as well as higher tubes loading. However, the addition of nanotubes resulted in the glass transition degradation of the resulting nanocomposites. This thesis research developed new methods of dispersion and fabrication of nanotube composites, which considerably enhances tube dispersion and mechanical properties of the resultant nanocomposites. The results also reveal that modified tubes using the selected functionalization methods can be used to improve both tube dispersion and interface bonding in the nanocomposites.
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Date Issued: 2003
Identifier: FSU_migr_etd-1383
Format: Thesis

Title: Processing-Structure-Property Relationships of Carbon Nanotube and Nanoplatelet Enabled Piezoresistive Sensors.
Creator: Luo, Sida, Liu, Tao, Brooks, James, Zhang, Chuck, Zhang, Mei, Shanbhag, Sachin, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Individual carbon nanotubes (CNTs) possess excellent piezoresistive performance, which is manifested by the significant electrical resistance change when subject to mechanical deformation. In comparison to individual CNTs, the CNT thin films, formed by a random assembly of individual tubes or bundles, show much lower piezoresistive sensitivity. Given the progress made to date in developing CNT ensemble based-piezoresistive sensors, the related piezoresistive mechanism(s) are still not well...
Show moreIndividual carbon nanotubes (CNTs) possess excellent piezoresistive performance, which is manifested by the significant electrical resistance change when subject to mechanical deformation. In comparison to individual CNTs, the CNT thin films, formed by a random assembly of individual tubes or bundles, show much lower piezoresistive sensitivity. Given the progress made to date in developing CNT ensemble based-piezoresistive sensors, the related piezoresistive mechanism(s) are still not well understood. The crucial step to obtain a better understanding of this issue is to study the effects of CNT structure in the dispersion on the piezoresistivity of CNT ensemble based-piezoresistive sensors. To reach this goal, my Ph.D. research first focuses on establishing the processing-structure-property relationship of SWCNT thin film piezoresistive sensors. The key accomplishment contains: 1) developing the combined preparative ultracentrifuge method (PUM) and dynamic light scattering (DLS) method to quantitatively characterized SWCNT particle size in dispersions under various sonication conditions; 2) designing combined ultrasonication and microfluidization processing protocol for high throughput and large-scale production of high quality SWCNT dispersions; 3) fabricating varied SWCNT thin film piezoresistive sensors through spray coating technique and immersion-drying post-treatment; and 4) investigating the effect of microstructures of SWCNTs on piezoresistivity of SWCNT thin film sensors. This experimental methodology for quantitative and systematic investigation of the processing-structure-property relationships provides a means for the performance optimization of CNT ensemble based piezoresistive sensors. As a start to understand the piezoresistive mechanism, the second focus of my Ph.D. research is studying charge transport behaviors in SWCNT thin films. It was found that the temperature-dependent sheet resistance of SWCNT thin films could be explained by a 3D variable range hopping (3D-VRH) model. More importantly, a strong correlation between the length of SWCNTs and the VRH parameter T0, indicating the degree of disorder of the electronic system, has been identified. With the structure dependent transport mechanism study, a very interesting topic - how T0 changes when SWCNT thin film is under a mechanical deformation, would be helpful for better understanding the piezoresistive mechanism of SWCNT thin film sensors. As demonstrated in transport mechanism study, SWCNT thin film exhibits a negative temperature coefficient (NTC) of resistance. In contrast, another family of carbon nanomaterials, graphite nanoplatelets (GNPs), shows positive temperature coefficient (PTC) of resistance, attributed to their metallic nature. Therefore, upon a wise selection of mass ratio of SWCNTs to GNPs for fabrication of hybrid SWCNT/GNP thin film piezoresistive sensors, a near zero temperature coefficients of resistance in a broad temperature range has been achieved. This unique self-temperature compensation feature along with the high sensitivity of SWCNT/GNP hybrid sensors provides them a vantage for readily and accurately measuring the strain/stress levels in different conditions. With the unique features of SWCNT/GNP hybrid thin film sensors, my future work will focus on application exploration on SWCNT/GNP thin film sensor based devices. For example, we have demonstrated that it is potential for man-machine interaction and body monitoring when coating the hybrid sensor on highly stretchable nitrile glove. The structure health monitoring (SHM) of composite materials could also be realized by coating the thin film sensor on a glass fiber surface and then embedding the fiber sensor in composite structure.
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Date Issued: 2013
Identifier: FSU_migr_etd-7478
Format: Thesis

Title: Performance of Control Charts for Weibull Processes.
Creator: Zhang, Mang, Pignatiello, Joseph J., Awoniyi, Samuel A., Vanli, Arda, Okoli, Okenwa, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Statistical Process Control (SPC) is a statistical method for monitoring variability of processes. Process variation can be categorized as common cause and special cause. Common causes are the natural or expected variation of some change in the process. The presence of a special cause indicates that the process is not in a state of statistical control. The SPC methodology dictates that a search should be initiated when a special cause is detected. This thesis is about the set-up of magnitude...
Show moreStatistical Process Control (SPC) is a statistical method for monitoring variability of processes. Process variation can be categorized as common cause and special cause. Common causes are the natural or expected variation of some change in the process. The presence of a special cause indicates that the process is not in a state of statistical control. The SPC methodology dictates that a search should be initiated when a special cause is detected. This thesis is about the set-up of magnitude robust control chart and CUSUM charts for detecting changes in Weibull processes. The research includes the comparison of the ARL performance of the control charts.
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Date Issued: 2009
Identifier: FSU_migr_etd-0537
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: 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: Model Characteristics and Properties of Nanorobots in the Bloodstream.
Creator: Zimmer, Michael Makoto, Owusu, Yaw A., Roberts, Rodney G., Parker, Reginald, Zhang, Chun, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Many researchers have various visions and concepts about what the nanorobot will be like and what they will do. Most people see nanorobots doing a lot of functions in the medical field, having ideas of them doing cell repair, seek-and-destroy harmful diseases, clean arteries of cholesterol buildup, and much more. There are many questions that need to be answered as to what exactly is needed for the nanorobot to perform these medical functions. This project is not interested in the design of...
Show moreMany researchers have various visions and concepts about what the nanorobot will be like and what they will do. Most people see nanorobots doing a lot of functions in the medical field, having ideas of them doing cell repair, seek-and-destroy harmful diseases, clean arteries of cholesterol buildup, and much more. There are many questions that need to be answered as to what exactly is needed for the nanorobot to perform these medical functions. This project is not interested in the design of the nanorobot, but focuses on the characteristics and parameters that should be considered for a nanorobot to function through the bloodstream of a human body, specifically. To do this, a mobile robot was being used to traverse through a scaled model of the bloodstream. The scale model consisted of clear tubing or piping enclosed in a loop filled with liquid to nearly the exact viscosity of blood. The liquid had particles to emulate the various obstacles that a nanorobot would encounter like red blood cells and other molecules. The simulation had a continuous flow at the appropriate rate and pressure expected in the bloodstream. The pipe size was calculated setting the ratio of the diameter of a particular blood vessel over the diameter face of the assumed size of a nanorobot (DBV / DNR) equaling the diameter of the pipe (unknown variable) to the diameter face of the mobile robot (DPipe / Dsub). The pipe size came to be 6.66 inches, however pipe sizes come in increments of 2 inches larger than 4 inch pipes. It was settled to use 6 inch pipes. With this variable, the Reynolds number is the diameter of pipe times the velocity of the fluid over the kinematic viscosity of the fluid (R = (DPipe * ν) / υ). Setting the Reynolds value of the bloodstream equal to the Reynolds value of the model, the velocity of the pipe could be isolated. With that the flow rate was evaluated by multiplying the velocity to the cross-sectional area of the pipe (Flow Rate was equal to 0.2021392 gallon/minute). With all conditions met for an accurate model of the bloodstream, the physical model was designed and constructed then testing with the mobile robot was done to determine how the robot functions in the simulated environment. The results of the experiment showed that the mobile robot is influenced by the environment. The speed it travels decreases as viscosity of the fluid increases. The particles in the fluid also affect the speed along with the flow of the fluid. Mobility and control of the mobile robot were hindered with the increase of viscosity and the presence of particles. When traveling against the flow of the fluid it was further hindered. Stability of the craft increased along with viscosity but was chaotic traveling with particles. The performance of the mobile robot was affected by the conditions and parameters involved in the bloodstream.
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Date Issued: 2005
Identifier: FSU_migr_etd-0496
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: Modeling, Design and Control of Vacuum Assisted Resin Transfer Molding (VARTM) for Thickness Variation Reduction.
Creator: Li, Jing, Zhang, Chuck, Wang, Ben, Gunzburger, Max, Okoli, Okenwa, Liang, Zhiyong, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: In general, composite manufacturing processes have more variations compared to the metal manufacturing processes due to the larger raw material and manufacturing processes variations. Vacuum-assisted resin transfer molding (VARTM), one of a commonly used composite manufacturing processes, is becoming more popular due to its low cost tooling and environmental friendly operating conditions. Currently, most commercial products manufactured by VARTM are developed based on the user's experience...
Show moreIn general, composite manufacturing processes have more variations compared to the metal manufacturing processes due to the larger raw material and manufacturing processes variations. Vacuum-assisted resin transfer molding (VARTM), one of a commonly used composite manufacturing processes, is becoming more popular due to its low cost tooling and environmental friendly operating conditions. Currently, most commercial products manufactured by VARTM are developed based on the user's experience and involve repeated experiments. To optimize the process, reduce manufacturing costs, and maintain consistent part quality, knowledge of mold filling, especially flow through thickness direction is required. This dissertation investigates the mechanism of the thickness variation and quantifies the magnitudes of the thickness distribution. Typically, thickness gradient and variations of VARTMed parts result from material variations and the infusion pressure gradient during the process. After infusion, certain amount of pressure gradient is frozen into the preform, which primarily contributes to the thickness variation. This research investigates the mechanism of the thickness variation dynamic change during the infusion and curing/relaxing processes. A numerical model was developed to track the thickness change of the bagging film free surface. A time-dependent permeability model as a function of compaction pressure was incorporated into an existing resin transfer molding code for obtaining the initial conditions of curing/relaxing process. Control volume (CV) and volume of fluid (VOF) methods were combined to solve the free surface problem. In addition, this dissertation analyzes the sources of the uncertainties and quantifies the magnitudes of the uncertainties by error propagation theory to characterize the statistical properties of the permeability values. Normal distribution and Weibull distribution were utilized as the statistical models for representing the average permeability values and race-tracking effects, respectively. Factors related to the part thickness variation were identified with design of experiments method and a better tooling design was obtained by configuring the different flow media. With the help of the simulation program, a process model-based tooling design optimization was formulated. However, the parameter uncertainty made the deterministic optimization unreliable. To address the issue of part-to-part thickness variation, a stochastic process simulation coupled with optimization was proposed and demonstrated.
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Date Issued: 2006
Identifier: FSU_migr_etd-1440
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: Assessment of Triboluminescent Materials for In-Situ Health Monitoring.
Creator: Dickens, Tarik Jamel, Okoli, Okenwa, Liang, Zhiyong, Simpson, James, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Advanced composites which offer robust mechanical properties are being increasingly used for structural applications in the aerospace, marine, defense and transportation industries. However, the anisotropic nature of composite materials leaves it susceptible to problematic failure; the development of means for detecting failure is imperative. As design and functionality requirements of engineering structures such as spacecraft, aircraft, naval vessels, buildings, dams, bridges and ground...
Show moreAdvanced composites which offer robust mechanical properties are being increasingly used for structural applications in the aerospace, marine, defense and transportation industries. However, the anisotropic nature of composite materials leaves it susceptible to problematic failure; the development of means for detecting failure is imperative. As design and functionality requirements of engineering structures such as spacecraft, aircraft, naval vessels, buildings, dams, bridges and ground-based vehicles become more complex; structural health monitoring (SHM) and damage assessment is becoming more rigorous. Though structures involved have regular costly inspections, the damage associated with composites in SHM systems can lead to catastrophic and expensive failures. Industry and research have no single technique used on its own to provide reliable results. Integrating several nondestructive evaluation (NDE) techniques could provide a solution for real-time health monitoring. Such studies, utilizing acoustic emission (AE), A-scans, C-scans, and laser shearography have reported considerable success. Nevertheless, damage detection has to be reliable and cost effective. The answer may lie with the development of SHM systems by the use of triboluminescent crystals, as well as optical fibers embedded in the composite matrix. These crystals react to straining or fracture by emitting light of varied luminous intensity. Thus, a fiber-reinforced plastic (FRP) laminate doped with Triboluminescent (TL) or Mechanoluminescent (ML) crystals, acting as health sensors to its host material, will give an indication of crack initiation well ahead of catastrophic failure(s). The development of an in-situ health monitoring system for safety critical structures is a viable route through 'Triboluminescence'. Assessing the viability of a proposed structural sensor system requires cross-linking between key areas in science and engineering. Initial testing has shown that light can propagate through doped resins alone, as well as doped FRP laminates. The luminous intensities relation to impact velocity adds credence to a monitoring system that can characterize impact activity. However, Triboluminescent crystals have high material density. In response, a two-dimensional rotational mold was built to counteract massive settling under normal vacuum molding processes. Micro-structural evaluations using scanning electron microscopy (SEM) and EDAX imaging have aided in demystifying particulate dispersion of TL fillers through use of image processing.
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Date Issued: 2007
Identifier: FSU_migr_etd-0734
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: 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: Design and Analysis of Response Surface Designs with Restricted Randomization.
Creator: Wesley, Wayne R., Simpson, James R., Srivastava, Anuj, Parker, Peter A., Pignatiello, Joseph J., Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Many industrial experiments are conducted under various conditions which do not facilitate complete randomization of all the experimental factors. In response surface methodology whenever there are restrictions on randomization the experimental procedure usually follows the split plot design approach. Split plot designs are used when there are factors which are difficult or costly to change or adjust during an experiment. Split plot designs are currently generating renewed interest because of...
Show moreMany industrial experiments are conducted under various conditions which do not facilitate complete randomization of all the experimental factors. In response surface methodology whenever there are restrictions on randomization the experimental procedure usually follows the split plot design approach. Split plot designs are used when there are factors which are difficult or costly to change or adjust during an experiment. Split plot designs are currently generating renewed interest because of their usefulness and practical application in industrial settings. Despite the work accomplished through various research efforts, there is still a need to understand the optimality properties of these designs for second-order response surface models. This dissertation provides the development of an analytical approach for the computation of various optimality properties for the assessment of second-order split plot designs. The approach involves a thorough investigation of the impact of restricted randomization on the information matrix, which characterizes much of the relationship between the design points and the proposed response surface model for split plot designs. Several important insights are presented for the construction of second-order split plot designs. In addition, the analytical equations reported compute exact design optimality values and are more efficient than currently available methods. A particular feature of these analytical equations is that they are functions of the design parameters, radius and variance ratio. Further, a significant result is the ability to efficiently compute the exact value of the integrated prediction variance for both split plot designs and completely randomized designs. The functionality of the computational procedures presented provides easy evaluation of the impact of changes in the design structure and variance ratio on the optimality properties of second-order split plot designs.
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Date Issued: 2006
Identifier: FSU_migr_etd-1180
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: 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: 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: 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: Application of Experimental Design for Efficient Wind Tunnel Testing: The Tandem Wing Mav Case.
Creator: English, Teresa Gail, Simpson, James R., Landman, Drew, Okoli, Okenwa I., Pignatiello, Joseph J., Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Micro air vehicles (MAVs) are small scale unmanned aerial vehicles (UAVs) that are used for reconnaissance, intelligence gathering and battle damage assessment. The U.S. Air Force Research Lab Munitions Directorate develops MAVs for various defense missions. The case involves a tandem wing MAV that is designed to have retractable wings for transport, control surfaces on the aft wing, and two different vertical tail configurations. Wind tunnel testing is one of the vital steps in MAV...
Show moreMicro air vehicles (MAVs) are small scale unmanned aerial vehicles (UAVs) that are used for reconnaissance, intelligence gathering and battle damage assessment. The U.S. Air Force Research Lab Munitions Directorate develops MAVs for various defense missions. The case involves a tandem wing MAV that is designed to have retractable wings for transport, control surfaces on the aft wing, and two different vertical tail configurations. Wind tunnel testing is one of the vital steps in MAV development for evaluating and ensuring that stability and control requirements are met for sustained flight. Traditionally, wind tunnel tests have been performed using a one factor at a time (OFAT) approach. Wind tunnel OFAT involves testing at many levels of one particular factor, usually angle of attack (AoA), while holding all other input factors constant; this technique is then repeated for various input factor configurations. This classic approach can be useful in determining the effect that each input alone has on the desired response. However, OFAT is not capable of identifying the influence that inputs interacting with one another have on the response, which commonly affect aircraft performance. Furthermore, OFAT is not capable of characterizing uncertainty that is present in experimentation. The research objective is to develop a testing strategy that provides an efficient number of test points to run in the wind tunnel effectively characterizing the aerodynamic behavior of MAVs as a function of design changes, changes in attitude and control inputs, while reducing costs and resources using design of experiments (DOE) and response surface methods (RSM). The research involves one of the first applications of second-order split plot designs, as well as the traditional completely randomized design. The DOE/RSM approach will be directly compared to the traditional OFAT wind tunnel testing that is performed during the same test period. The analyses resulting from the DOE/RSM approach will highlight its capabilities in identifying factor interactions, characterizing system uncertainty, and providing stability and control analyses – the common objectives of wind tunnel testing. The outcome of the study will demonstrate the effectiveness of DOE/RSM techniques when tailored to meet the specifications of wind tunnel testing. Some characteristics involved with the wind tunnel environment are low noise, qualitative factors, hard-to-change factors, and second-order models. The collaboration of experimental design techniques adapted to traditional wind tunnel testing techniques will provide a powerful approach to characterizing and optimizing aerodynamic systems.
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Date Issued: 2007
Identifier: FSU_migr_etd-0559
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: Characterizing the Single-Walled Carbon Nanotube Dispersions: Novel Methods Development and Their Applications.
Creator: Xiao, Zhiwei, Liu, Tao, Ramakrishnan, Subramanian, Liang, Zhiyong, Guan, Jingjiao, Zhang, Mei, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Single-walled carbon nanotubes (SWCNTs) thin films exhibit great potential in various applications thanks to their extraordinary physical and mechanical properties. However, to fully take advantage of their superior properties there are still several barriers to be overcome. On one hand, SWCNTs are rarely found as isolated individual tubes, which makes them very difficult to exfoliate and disperse. On the other hand, SWCNTs are not with perfect defect-free chemical structure, which can...
Show moreSingle-walled carbon nanotubes (SWCNTs) thin films exhibit great potential in various applications thanks to their extraordinary physical and mechanical properties. However, to fully take advantage of their superior properties there are still several barriers to be overcome. On one hand, SWCNTs are rarely found as isolated individual tubes, which makes them very difficult to exfoliate and disperse. On the other hand, SWCNTs are not with perfect defect-free chemical structure, which can severely degrade the intrinsic properties of the pristine SWCNTs and thus deteriorate the various SWCNT based applications. In many cases, when people perform chemical functionalization to SWCNTs, they have to find a balance between the improvement of the dispersability and compatibility of SWCNTs and the degradation of the intrinsic properties of SWCNTs. Therefore, it is crucial to have an easy-to-use and reliable way to characterize and quantify the corresponding structural information of SWCNT in dispersion such as bundle size, bundling state, defect density, etc. Two different techniques for in-situ structural characterization of SWCNTs in dispersion have been developed. The Preparative Ultracentrifuge Method (PUM) combined with dynamic light scattering (DLS) technique provides us an approach to investigate the bulk averaged SWCNT bundle size in dispersion. The Simultaneous Raman Scattering and Photoluminescence (SRSPL) technique allows us to study the bundling state/degree of exfoliation of SWCNT in dispersion. Based on the 1D exciton diffusion model, we can also use the SRSPL technique to estimate the defect density of SWCNTs in dispersion. The application of PUM and SRSPL has been demonstrated in studying the structural changes of SWCNT dispersion under different processing (sonication and ultracetrifugation) conditions. It revealed the exfoliation mechanism of SWCNT under sonication technique. Moreover, the developed PUM characterization techniques were further applied to study the interactions between SWCNT and polyacrylonitrile (PAN) homo- and copolymers. On the basis of the established PUM and SRSPL characterization methods, my proposed work focuses on an in-depth understanding of the effects of bundling states and defect density on the electrical and mechanical properties of SWCNT thin films. The detailed proposed tasks include: 1) improve the current physical model for quantifying defect density; 2) prepare and characterize the SWCNT dispersions with controlled bundle size and defect density; 3) fabricate and characterize the electrical and mechanical properties of SWCNT thin films to elucidate the effects of bundling state and defect density of SWCNTs in the dispersion.
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Date Issued: 2013
Identifier: FSU_migr_etd-7670
Format: Thesis

Title: Integrated Robust Design Using Computer Experiments and Optimization of a Diesel HPCR Injector.
Creator: Meng, Jikui, Zhang, Chuck, Buzyna, George, Wang, Ben, Eckerle, Wayne A., Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Robust design has been gaining plenty of attention in both academia and industry over the past two and half decades. However, there is still plenty of room for improvement. In this dissertation research, several drawbacks of the existing robust design methods were identified and analyzed. These shortcomings mainly include incompatible robust parameter design and tolerance design optima, inadequate attention to internal noise factors, limitation of Steepest Descent search in parameter design...
Show moreRobust design has been gaining plenty of attention in both academia and industry over the past two and half decades. However, there is still plenty of room for improvement. In this dissertation research, several drawbacks of the existing robust design methods were identified and analyzed. These shortcomings mainly include incompatible robust parameter design and tolerance design optima, inadequate attention to internal noise factors, limitation of Steepest Descent search in parameter design process, limitation of robust design using computer experiments, limitation with the Loss Function, and insufficient connection between the academia and industry on robust design. An integrated robust design framework was proposed to help achieve robustness against both external and internal noises. A Steepest Descent Driven Parameter Design method was developed to enhance parameter design. Also developed was an improved loss function for robust tolerance design. The proposed methodology was applied using computer simulation experiments to optimize the design of a state-of-the-art injector in a High Pressure Common Rail (HPCR) injection system in a diesel engine. The injector simulation model was built using Advanced Continuous Simulation Language (ACSL) and well calibrated through extensive hardware experiments. iSIGHT, an integration and optimization software package, was utilized to assist the computer experiments. Design Experts and Minitab were used to conduct statistical designs and analysis. It was demonstrated that the injector performance was significantly improved with the proposed method. The proposed method was also compared with Taguchi's method and Response Surface Methodology based robust design method.
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Date Issued: 2006
Identifier: FSU_migr_etd-2486
Format: Thesis

Title: Investigation and Characterization of SWNT Buckypaper Manufacturing Process.
Creator: Lin, Chih-Yen, Liang, Zhiyong, Wang, Ben, Okoli, Okenwa, Zhang, Chuck, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: For developing high performance carbon nanotube-reinforced polymer composites, uniform nanotube dispersion, good nanotube/matrix wetting and interfacial bonding, controlled alignment and high tube loading are critical issues. A novel technical approach using a unique buckypaper/resin infiltration method has been developed at Florida Advanced Center of Composite Technologies (FAC2T) to fabricate nanocomposites with controlled tube dispersion, orientation, and high SWNT loading. Buckypapers are...
Show moreFor developing high performance carbon nanotube-reinforced polymer composites, uniform nanotube dispersion, good nanotube/matrix wetting and interfacial bonding, controlled alignment and high tube loading are critical issues. A novel technical approach using a unique buckypaper/resin infiltration method has been developed at Florida Advanced Center of Composite Technologies (FAC2T) to fabricate nanocomposites with controlled tube dispersion, orientation, and high SWNT loading. Buckypapers are thin membranes or films of preformed networks of well-dispersed SWNTs. The preformed SWNT networks are eventually transformed in the nanocomposites to construct final nanostructures in the materials. Therefore, quality buckypapers are vital for developing high performance nanocomposites. This research focuses on systematically investigating buckypaper fabrication process and characterizing the resulting buckypapers for better understanding the process and building databases of both randomly oriented and magnetically aligned buckypaper materials. The results show that the formation of buckypaper during suspension filtration can be divided into three stages: free deposition, network formation and thickness build-up. Each stage has different filtration flow rate. The results also indicated that the average thickness, weight, and area density of the aligned buckypapers are smaller than that of the random buckypapers, while the average cubic density of the aligned buckypapers is higher than that of the random buckypapers. Due to possible re-assembly of nanotubes during magnetic alignment, the average rope size of the aligned buckypapers is larger than that of the random buckypapers, and its nanostructure also has relatively larger average pore size. Furthermore, the study of cleaning residual surfactant in the produced buckypapers was also conducted. The results show 70% of the surfactant can be removed by using the proposed cleaning method.
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Date Issued: 2005
Identifier: FSU_migr_etd-1341
Format: Thesis

Title: Investigation of Vartm Processing of High Temperature RP-46 Resin System.
Creator: Prasad, Thammiah M., Zhang, Chuck, Okoli, Okenwa, Liang, Zhiyong, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: The advantages of using polymer matrix composites in various applications are very well known throughout many industries. Their introduction and subsequent development since the 1940's has led to major cost savings due to their lightweight and excellent mechanical properties. Off late, product designers have been taking advantage of improved thermal properties (CTE, thermo-oxidative stability) that these composite materials have to offer. This began with the development of PMR-15, a high...
Show moreThe advantages of using polymer matrix composites in various applications are very well known throughout many industries. Their introduction and subsequent development since the 1940's has led to major cost savings due to their lightweight and excellent mechanical properties. Off late, product designers have been taking advantage of improved thermal properties (CTE, thermo-oxidative stability) that these composite materials have to offer. This began with the development of PMR-15, a high temperature polyimide resin back in the 1970's. The aerospace industry has increasingly turned towards high temperature polymer matrix composites (HTPMC) to replace other heavier materials in engine components thus improving the thrust to weight of the engine. But, PMR-15 has a major drawback related to high safety standards that are needed during processing. The implementation of these controls during processing resulted in huge costs to the industry. This led to the development of a new polyimide high temperature resin system called RP-46 at NASA Langley research center. RP-46 has excellent thermal and mechanical properties comparable to PMR-15 and is safer to handle due to the absence of the lethal MDA monomer, a carcinogen. This research investigates the issues related to processing of RP-46 resin system using the Vacuum Assisted Resin Transfer Molding (VARTM) process, a cost effective method for manufacturing composite materials. The entire process is setup keeping in consideration the requirement of high temperature environments for processing of RP-46. A number of initial trials helped understand the dynamics of the process and identify critical factors and key parameters. The various laminates that were made were tested for mechanical properties (ASTM D3039 - Tensile strength and modulus) and thermal properties (Dynamic Mechanical Analysis, Thermal Mechanical Analysis, Thermal Gravimetric Analysis) were performed and the results were compared with RP-46 samples made using autoclave processing. Although the VARTM laminates had issues related to void contents and the release of volatiles during the infusion stage of the process, the VARTM process was found to be feasible to make composites with RP-46.
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Date Issued: 2004
Identifier: FSU_migr_etd-0441
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

Title: Functionalization of Carbon Nanotubes: Characterization, Modeling and Composite Applications.
Creator: Wang, Shiren, Liang, Zhiyong, Brooks, James, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Single walled carbon nanotubes (SWNTs) have demonstrated exceptional mechanical, thermal and electrical properties, and are regarded as one of the most promising reinforcement materials for the next generation of high performance structural and multifunctional composites with tremendous application potentials. However, to date, most application attempts have been hindered by several technical roadblocks, such as poor dispersion and weak interfacial bonding. Functionalization of nanotubes was...
Show moreSingle walled carbon nanotubes (SWNTs) have demonstrated exceptional mechanical, thermal and electrical properties, and are regarded as one of the most promising reinforcement materials for the next generation of high performance structural and multifunctional composites with tremendous application potentials. However, to date, most application attempts have been hindered by several technical roadblocks, such as poor dispersion and weak interfacial bonding. Functionalization of nanotubes was suggested to be an effective way to overcome these technical issues and then to realize the full potential of nanotubes as reinforcement materials. In this dissertation, several original functionalization methods were proposed, studied, analyzed and quantitatively compared. These functionalization methods included precision sectioning of nanotubes using an ultra-microtome, electron-beam irradiation, amino-group grafting, and epoxide group grafting. Short nanotubes with open-ends show rich chemistry, ballistic transportation properties and capability of good dispersion. However, current reported cutting methods are difficult to protect tube sidewalls from devastation and to achieve desired length control. This research has developed a technique to precisely section aligned SWNT membranes through ultra-microtome in order to produce short and open-end tubes. Aligned SWNT membranes were sectioned to 50nm and 200nm. The results of AFM characterization and length statistical analysis have found the measured lengths were centered at 87nm and 246nm, respectively. Raman and TEM characterization results confirmed the minimized damage to the sidewalls. The cut-SWNTs were applied to nanocomposites fabrications. Young's modulus and strength of the composite were improved by 20% and 7%, respectively, when using 0.5wt% cut-SWNTs. The SEM results also confirmed the improvement in dispersion. The enhanced tensile strength indicates that load-transfer was improved due to the enhanced interfacial bonding. This dissertation also proposed a unique covalent sidewall functionalization through epoxy-grafting. The characterizations of Raman, FT-IR and TEM have proved the successful grafting of epoxide-group to the carbon nanotubes. The SEM results of the epoxy-grafted SWNTs reinforced composite indicated that significant improvement of dispersion was achieved. Dynamic Raman tests also revealed the considerable enhancement in the interfacial bonding. The tensile strength of nanocomposites was enhanced 27.1% and Young's modulus 30% with only 0.5wt% loading of epoxy-grafted SWNTs. When composites were fabricated with 1wt% loading of epoxy-grafted SWNTs, the strength and Young's modulus were improved by 40.3% and 60%, respectively. These substantial improvements are among the highest in the reported literatures. Furthermore, this research also succeeded in grafting amino-group onto SWNT sidewalls through one-step diazotization. Improvements in both dispersion and interfacial bonding were achieved. Young's modulus and strength for the amino-functionalized SWNTs composites with 0.5wt% loading were enhanced by 25% and 21.9%, respectively. The electron beam irradiation on the thin SWNTs membrane was both experimentally and theoretically investigated. Experimental results suggested that there exists a critical dose of irradiation in acquiring a desirable cross-linkage, above which significant enhancement of the SWNT membranes properties can be acquired. The theoretic modeling indicates that the density of cross-linkage is a quadratic function of the irradiation dosages. The irradiation-induced inter-tube bridging significantly enhanced the Young's modulus and tensile strength of the SWNTs membrane by 2 folds and 6 folds, respectively. Electric conductivity was also increased more than 1 fold. Both mechanical and electric properties improvements make the irradiated SWNT membranes very promising in the versatile applications, including electronic device, energy storage, biomaterials, and nanocomposites. All the methods developed in the dissertation demonstrated effectiveness in improving dispersion and interfacial bonding, resulting in considerable improvements in composite mechanical properties. Modeling of functionalization provided in-depth understanding and offered reasonable explanations of SWNTs length distribution, as well as carbon nanostructure transformation upon electron-beam irradiation. Both experimental and theoretical investigations would facilitate full realization of the potential of nanotubes-reinforced nanocomposites.
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Date Issued: 2006
Identifier: FSU_migr_etd-1253
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: 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: Nanotube and Nanofiber Buckypaper Cold Cathode Illumination: Experimental Investigation.
Creator: Chen, Yi Wen (Evin), Wang, Ben, Liang, Zhiyong, Zhang, Chuck, Park, Young-Bin, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Since the first Cathode Ray Tube (CRT) TV was invented in 1927, display technology has progressed at a rapid speed, attracting tremendous attention and enormous resources. Liquid Crystal Display (LCD) is the most mature and popular technology in flat panel displays compared to CRT. Carbon nanotube backlight unit (CNT-BLU) was regarded as a strong contender to replace the cold cathode fluorescence lamp backlight unit (CCFL-BLU) in LCD. CNTs have been spotlighted as one of promising...
Show moreSince the first Cathode Ray Tube (CRT) TV was invented in 1927, display technology has progressed at a rapid speed, attracting tremendous attention and enormous resources. Liquid Crystal Display (LCD) is the most mature and popular technology in flat panel displays compared to CRT. Carbon nanotube backlight unit (CNT-BLU) was regarded as a strong contender to replace the cold cathode fluorescence lamp backlight unit (CCFL-BLU) in LCD. CNTs have been spotlighted as one of promising alternatives for new electron sources; small tips and large aspect ratios of CNTs allow for a large electric field enhancement that makes them ideal field emitters. In this research, nanotube network BuckyPaper was proposed to act as surface luminary source for BLU. The major objective of this research is to systematically characterize various field emission properties of BuckyPapers and various lengths of open-ended CNTs. Particularly, low turn-on voltage, high average current, high luminance, low power consumption, uniformity and longer life-span will be explored. VGCNF/SWNT in ratio 1:1 BuckyPaper film demonstrated the lowest turn-on voltage (0.623 V/um) and randomly dispersed SWNT BuckyPaper film showed the largest enhancement factor value (1062) among all BuckyPaper samples. The structure of emitters might be the major reason for the varying results from different compositions of BuckyPaper films. The 400 nm open-ended SWNT paste showed the lowest turn on voltage at 0.313 V/um and the largest enhancement factor value (3470). Open-ended SWNT paste exhibited the best I-V properties, but did not demonstrate acceptable durability. The effect of varying aspect ratio of open-ended SWNT will be investigated in the future.
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Date Issued: 2006
Identifier: FSU_migr_etd-3858
Format: Thesis

Title: Nanowire Alignment and Patterning via Evaporation-Induced Directed Assembly.
Creator: Abdelsalam, Farag, Zhang, Mei, Okoli, Okenwa, Liang, Zhiyong Richard, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: The post synthetic assembly of nanowires into desired configurations presents a unique challenge. The inherent size of nanowires does not lend it self to a method or process capable of easily arranging or manipulating these materials. The recent understanding of how contact-line deposition, or the "coffee-ring effect", influences isotropic particles has lead to interest in investigating its influence over nanowires. Research has shown that nanowires can be aligned and selectively deposited at...
Show moreThe post synthetic assembly of nanowires into desired configurations presents a unique challenge. The inherent size of nanowires does not lend it self to a method or process capable of easily arranging or manipulating these materials. The recent understanding of how contact-line deposition, or the "coffee-ring effect", influences isotropic particles has lead to interest in investigating its influence over nanowires. Research has shown that nanowires can be aligned and selectively deposited at the edge of a drying droplet as a result of evaporation-induced capillary flow. From this basic understanding several methods have developed with the intent of producing a facile, robust, and scalable nanowire assembly process. This work provides insight into the coffee-ring effect and the mechanisms that draw from it to align, assemble, and pattern nanowire structures prior to introducing and providing the results of a new contact line deposition method.
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Date Issued: 2011
Identifier: FSU_migr_etd-4679
Format: Thesis

Title: On the Use of a Novel Recuperative Nanofluid Heat Transfer Methodology for Improving Photovoltaic Output Power in Residential and Industrial Applications.
Creator: Anthony, Thomas P., Pignatiello, Joseph J., Vanli, Arda, Roberts, Rodney, Zhang, Mei, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: ABSTRACT Since there has been an increase in the price of petroleum, there has been an increased need for photovoltaic systems over the last two decades. An increased number of private citizens are attracted to photovoltaic (PV) power as a viable source of independent renewable energy. Presently there is a mandate to continually improve the performance of the PV panels to maintain sustainability and to develop next generation PV systems. Most PV manufacturers state specifications of PV panels...
Show moreABSTRACT Since there has been an increase in the price of petroleum, there has been an increased need for photovoltaic systems over the last two decades. An increased number of private citizens are attracted to photovoltaic (PV) power as a viable source of independent renewable energy. Presently there is a mandate to continually improve the performance of the PV panels to maintain sustainability and to develop next generation PV systems. Most PV manufacturers state specifications of PV panels in terms of standard testing condition (STC) of 25º C or 77º F. However, many panels are operated in environments where temperatures are well above the level of STC reaching as high as 180º F (76º C). This has been shown to reduce the solar panel energy conversion, particularly the power output of the panels. To date literature has shown that the use of two cooling methods, water and ambient air to remove heat from the panels has proven minimally effective. This research proposes a method of heat reduction employing a recuperative nanofluid heat transfer system. The system employs a labyrinth of nanofluid filled tubes along the back of the PV panel. Through a field experiment, four combinations of a copper nanofluid combinations acting as a heat transfer medium were employed to remove the excess heat incident on four experimental units. The removal of heat from the solar panels to reservoirs simulating a domestic or industrial water heater simultaneously reduced the temperature of the panel to promote increased power output as well as water heating. The analysis of the data showed an average increase in reservoir temperature of 25º F. An analysis showed that the proposed system is more economical than either standard PV systems or the use of municipal utilities. The hope is that the proposed system will reduce the average citizen's energy cost by at least 30 percent as well as enable private citizens and some industries to operate independent of the utility grid.
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Date Issued: 2012
Identifier: FSU_migr_etd-4695
Format: Thesis

Title: Multifunctional Multiscale Composites: Processing, Modeling and Characterization.
Creator: Qiu, Jingjing, Zhang, Chuck, Wang, Ben, Ramakrishnan, Subramanian, Liang, Zhiyong, Jack, David, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Carbon nanotubes (CNTs) demonstrate extraordinary properties and show great promise in enhancing in-plane and out-of-plane properties of traditional polymer/fiber composites and enabling functionality. However, current manufacturing challenges hinder the realization of their potential. In the dissertation research, both experimental and computational efforts have been conducted to investigate effective manufacturing techniques of CNT integrated multiscale composites. The fabricated composites...
Show moreCarbon nanotubes (CNTs) demonstrate extraordinary properties and show great promise in enhancing in-plane and out-of-plane properties of traditional polymer/fiber composites and enabling functionality. However, current manufacturing challenges hinder the realization of their potential. In the dissertation research, both experimental and computational efforts have been conducted to investigate effective manufacturing techniques of CNT integrated multiscale composites. The fabricated composites demonstrated significant improvements in physical properties, such as tensile strength, tensile modulus, inter-laminar shear strength, thermal dimension stability and electrical conductivity. Such multiscale composites were truly multifunctional with the addition of CNTs. Furthermore, a novel hierarchical multiscale modeling method was developed in this research. Molecular dynamic (MD) simulation offered reasonable explanation of CNTs dispersion and their motion in polymer solution. Bi-mode finite-extensible-nonlinear-elastic (FENE) dumbbell simulation was used to analyze the influence of CNT length distribution on the stress tensor and shear-rate-dependent viscosity. Based on the simulated viscosity profile and empirical equations from experiments, a macroscale flow simulation model on the finite element method (FEM) method was developed and validated to predict resin flow behavior in the processing of CNT-enhanced multiscale composites. The proposed multiscale modeling method provided a comprehensive understanding of micro/nano flow in both atomistic details and mesoscale. The simulation model can be used to optimize process design and control of the mold-filling process in multiscale composite manufacturing. This research provided systematic investigations into the CNT-based multiscale composites. The results from this study may be used to leverage the benefits of CNTs and open up new application opportunities for high-performance multifunctional multiscale composites.
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Date Issued: 2008
Identifier: FSU_migr_etd-2237
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: 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: 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: In-Mold Coating of Composites Manufactured with the Resin Infusion Between Double Flexible Tooling Process by Means of Co-Infusion.
Creator: Chiu, Posen, Okoli, Okenwa, Wang, Ben, Liang, Zhiyong, Zhang, Chuck, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: As composite materials gain wider acceptance within the transportation industry, it is pertinent to investigate the available coating processes with a view to reduce emissions and associated costs. Current painting processes are not only laborious and time consuming, but expensive and present safety issues. In-mold coating presents an avenue for eliminating on reducing theses problems. This work aims to determine the feasibility and develop a methodology for In-Mold Coating (IMC) components...
Show moreAs composite materials gain wider acceptance within the transportation industry, it is pertinent to investigate the available coating processes with a view to reduce emissions and associated costs. Current painting processes are not only laborious and time consuming, but expensive and present safety issues. In-mold coating presents an avenue for eliminating on reducing theses problems. This work aims to determine the feasibility and develop a methodology for In-Mold Coating (IMC) components manufactured using the Resin Infusion between Double Flexible Tooling (RIDFT) process. Comparisons of the cost and efficiency between a component manufactured by RIDFT and then painted, and a component manufactured by RIDFT IMC process is given. It indicates a 46% savings in capital investment and 55% savings in time while using RIDFT IMC. The viability of in-mold coating RIDFTed components was investigated. This work-in-process, reports on successes and challenges presented, during the co-infusion of a polyurethane enamel paint (DuPont Imron 5000) and a vinyl ester resin (Derakane 470-45). In this thesis, RIDFT IMC is used to manufacture a double-layered structure consisting of a vinyl ester layer for structural function and a polyurethane enamel coating layer. The two liquids are either simultaneously or sequentially infused into a double flexible mold and are cured. Liquid separation is maintained by a separation layer. Twenty-four case studies have been made to determine the viability of the IMC process. Eight different separation layers were tested to find out the most promising separating material. The specification of the separation layer was made. Several test evaluations were conducted. A Differential Scanning Calorimeter (DSC) is used to test the cure cycle for the resin and the paint. Mechanical testing, Dynamic mechanical analysis (DMA) and tensile tests are used to evaluate the performance of the produced parts. An Environmental Scanning Electron Microscope (ESEM) was used to evaluate the microstructure of the components. In order to improve the flow of the fluids, several Flow Distribution Channels (FDCs) were made and tested to determine the best configuration. The experimental results demonstrate that in-mold coating by means of co-infusion may be a viable option for painting RIDFT components with determination of an appropriate separation layer. The paint used in this work dissolves the separation layer. Further work has been suggested to develop a paint formulation that will not dissolve the separation layer.
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Date Issued: 2004
Identifier: FSU_migr_etd-3804
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: 2-D Reinforcement Structure for Fracture Strength and Fracture Toughness Enhancement for Alumina.
Creator: Ighodaro, Osayande Lord-Rufus, Okoli, Okenwa, Peterson-Hruda, Simone, Zhang, Mei, Liang, Zhiyong Richard, Department of Industrial and Manufacturing Engineering, Florida State...
Show moreIghodaro, Osayande Lord-Rufus, Okoli, Okenwa, Peterson-Hruda, Simone, Zhang, Mei, Liang, Zhiyong Richard, Department of Industrial and Manufacturing Engineering, Florida State University
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Abstract/Description: Despite the attractive properties of advanced ceramics, they are not popular for structural applications even though they possess high strength. Their low fracture toughness and brittle fracture mode are unwelcome for high integrity structure. Moreover, they fail at loads far below their theoretical strengths due to their inherent flaws. These have led to the development of reinforcing strategies to help enhance the fracture resistance of ceramics. However, reported strengths value are still...
Show moreDespite the attractive properties of advanced ceramics, they are not popular for structural applications even though they possess high strength. Their low fracture toughness and brittle fracture mode are unwelcome for high integrity structure. Moreover, they fail at loads far below their theoretical strengths due to their inherent flaws. These have led to the development of reinforcing strategies to help enhance the fracture resistance of ceramics. However, reported strengths value are still far below theoretical strength, most reinforced ceramics suffer trade-off between strength and toughness, and most present reinforcement methods are material specific. In this work, a generic method for reinforcing ceramic materials for the enhancement of fracture resistance is described. Continuous ductile ligaments oriented in two orthogonal directions and forming 2-D network grid reinforcement structure was employed. The method involves two major stages: fabrication of regular channels in 2-D in ceramic matrix to form the preform and infiltration of the preform with the required reinforcement. Two different materials: carbon fibers and soft metal alloys were used as sacrificial materials for fabricating the aligned 2-D regular channels in alumina matrix. After the porous preforms were formed, molten aluminum alloys were infiltrated into the channels by the application of mechanical pressure, and this completes the composite fabrication process. Mechanical tests show that some porous preforms having area fraction of 2.7 % exhibited 27 % higher flexural strength than the solid specimens despite the porosity contained and this has been attributed to the ability of the channels to reduce the population and distribution of cracks in the porous material. The reinforced composites were also subjected to mechanical tests which revealed 217.6 % enhancement in flexural strength for the 7.79 % Al 7075 alloy reinforced composite. This magnitude of property enhancement was achieved due to the confinement of the matrix in the loop of the reinforcement and the beneficial residual compressive stress generated as a result of the difference in coefficient of thermal expansion (CTE) of the alumina and aluminum. The residual compressive stress delays crack initiation and crack propagation in the alumina matrix. It also reduces the stress concentration factor in the matrix, leading to higher failure stress and higher fracture toughness.
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Date Issued: 2012
Identifier: FSU_migr_etd-5716
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: Electrical Properties of Carbon Nanotube Networks: Characterization, Modeling and Sensor Applications.
Creator: Li, Shu, Liang, Richard, Andrei, Petru, Vanli, Arda, Zhang, Chuck, Department of Industrial and Manufacturing Engineering, Florida State University
Abstract/Description: Carbon nanotubes (CNTs) possess extraordinary electrical properties including conductivity that is comparable to metals and breakdown current density that is orders of magnitude higher than copper. In order to take advantage of the electrical performance of CNTs in engineering applications, macroscopic carbon nanotube networks (NTN) are fabricated by entangling large amounts of CNTs into thin sheets. However, the electrical properties of these networks are much lower than those of individual...
Show moreCarbon nanotubes (CNTs) possess extraordinary electrical properties including conductivity that is comparable to metals and breakdown current density that is orders of magnitude higher than copper. In order to take advantage of the electrical performance of CNTs in engineering applications, macroscopic carbon nanotube networks (NTN) are fabricated by entangling large amounts of CNTs into thin sheets. However, the electrical properties of these networks are much lower than those of individual nanotubes. Stretch-induced alignment of CNTs is an effective approach to enhance the electrical conductivity of the NTNs. However, the alignment mechanism of NTNs during the stretching process has not been fully investigated. This study employed in-situ X-ray and Raman scattering techniques to characterize the NTN structural evolution during stretch-induced alignment. The observed inhomogeneous alignment of NTNs prompts the need for a method that accurately determines the degree of nanotube alignment in bulk materials. A method that combines X-ray scattering and electrical anisotropy measurement was explored and proposed to determine the aligned fractions of nanotubes. Based on the characterization results, the structure-property relationship of NTNs and their electrical conductivity was studied through a 3D physics-based electrical model. The model was built in two stages. First, the structural model of NTNs was built using coarse-grained molecular dynamics, which provides high fidelity representation of the waviness, contacts and self-assembly of constituent nanotubes and ropes that originated from the van der Waals interactions. By applying tensile strains, the dynamics model also enabled the direct simulation of the dynamics of networks aligned through stretching. After the network structure was established, the simulated NTNs were translated into equivalent electrical circuits. The electrical model was developed based on the Simulation Program with Integrated Circuit Emphasis, which allows us to directly conduct device design and analysis using NTNs. This model is able to capture the effects of alignment and contact changes on the electrical properties of NTNs. Based on the understanding of the unique contact resistance dominated transport mechanism of NTNs, sensor applications of the novel materials were explored. By manipulating the tunneling barrier through either polymer molecule insertion or increasing the tunneling distances, NTNs were studied for potential applications in detecting organic solvent leakage and sensing tensile strains. Scaling-up of sensor fabrication using aligned NTNs and advanced printing technology was also explored and demonstrated.
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Date Issued: 2012
Identifier: FSU_migr_etd-6957
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: Structural Health Monitoring with Lamb-Wave Sensors: Problems in Damage Monitoring, Prognostics and Multisensory Decision Fusion.
Creator: Mishra, Spandan, Vanli, Omer Arda, Okoli, Okenwa, Jung, Sungmoon, Park, Chiwoo, Florida State University, FAMU-FSU College of Engineering, Department of Industrial and...
Show moreMishra, Spandan, Vanli, Omer Arda, Okoli, Okenwa, Jung, Sungmoon, Park, Chiwoo, Florida State University, FAMU-FSU College of Engineering, Department of Industrial and Manufacturing Engineering
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Abstract/Description: Carbon ﬁber reinforced composites (CFRC) have several desirable traits that can be exploited in the design of advanced structures and systems. The applications requiring high strength- to-weight ratio and high stiﬀness-to-weight ratio such as, fuselage of airplanes, wind turbine blades, water-boats etc. have found profound use of CFRC. Furthermore, low density, good vibration damping ability, easy manufacturability, carbon ﬁber’s electrical conductivity, as well as high thermal conductivity...
Show moreCarbon ﬁber reinforced composites (CFRC) have several desirable traits that can be exploited in the design of advanced structures and systems. The applications requiring high strength- to-weight ratio and high stiﬀness-to-weight ratio such as, fuselage of airplanes, wind turbine blades, water-boats etc. have found profound use of CFRC. Furthermore, low density, good vibration damping ability, easy manufacturability, carbon ﬁber’s electrical conductivity, as well as high thermal conductivity and smooth surface ﬁnish provide additional beneﬁts to the users. Various applications of CFRC can be relevant for aerospace, military, wind-turbines, robotics, sports equipment etc. However, among many advantages of CFRC there are a few disadvantages; CFRC undergo completely diﬀerent failure patterns compared to metals. Once the yield strength is exceeded, CFRC will fail suddenly and catastrophically. The inherent anisotropic nature of CFRC makes it very diﬃcult for traditional condition monitoring methods to assess the condition of the structure. The complex failure patterns, including delamination, micro-cracks, and matrix-cracks require specialized sensing and monitoring schemes for composite structure. This Ph.D. research is focuses on developing an integrated structural health monitoring methodology for damage monitoring, remaining useful life estimation (RUL), and decision fusion using Lamb-wave data. The main objective of this research is to develop an integrated damage detection method that utilizes Lamb-wave sensor data to infer the state of the damage condition and make an accurate prognosis of the structure. Slow fatigue loading results in very unique failure patterns in the CFRC structures, fatigue damage ﬁrst manifests itself as ﬁber-breakage and then slowly progresses to matrix-cracks and that ultimately leads to delamination damage. This type of failure process is very diﬃcult to monitor using the traditionally used damage monitoring methods such as X-ray evaluation, ultrasonic evaluation, infrared evaluation etc. For this research, we have used principal component (PC) based multivariate cumulative sum (MCUSUM) to monitor the structure. MCUSUM chart is very useful when monitoring structures undergoing slow and gradual change. For remaining-useful-life (RUL) estimation, we have proposed to use the Wiener process model coupled with principal component regression (PCR). For damage detection/classiﬁcation we studied discriminant analysis, in-spite of the popular use in image analysis and in the gene data classiﬁcation problem, has not been widely used for damage classiﬁcation. In this research, we showed that discriminant analysis is a useful detecting known damage modes, while dealing with the high dimensionality of Lamb-wave data. We modiﬁed the standard Gaussian discriminant analysis by introducing regularization parameters to directly process raw Lamb-wave data without requiring an intermediate feature extraction step.
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Date Issued: 2016
Identifier: FSU_2016SU_Mishra_fsu_0071E_13346
Format: Thesis

Title: Process Modeling and Study of Carbon Nanotube Dispersion in Aqueous Suspensions.
Creator: Yang, Ming-Chia (Dawn), Liang, Zhiyong Richard, Spainhour, Lisa, Vanli, Omer Arda, Zeng, Changchun Chad, Florida State University, College of Engineering, Department of...
Show moreYang, Ming-Chia (Dawn), Liang, Zhiyong Richard, Spainhour, Lisa, Vanli, Omer Arda, Zeng, Changchun Chad, Florida State University, College of Engineering, Department of Industrial and Manufacturing Engineering
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Abstract/Description: Establishing accurate processing models to characterize and study the suspension preparation for manufacturing carbon nanotube (CNT) thin films or buckypaper (BP) is a challenging task. Acquiring a fundamental understanding of quantifiable dispersion quality and time-dependent dispersion quality changes during and after the dispersion processes of CNT suspensions are critical for many suspension-based CNT manufacturing processes. In this research, a novel in-line dispersion quality monitoring...
Show moreEstablishing accurate processing models to characterize and study the suspension preparation for manufacturing carbon nanotube (CNT) thin films or buckypaper (BP) is a challenging task. Acquiring a fundamental understanding of quantifiable dispersion quality and time-dependent dispersion quality changes during and after the dispersion processes of CNT suspensions are critical for many suspension-based CNT manufacturing processes. In this research, a novel in-line dispersion quality monitoring system was developed. The monitoring was carried out using an integration of dynamic light scattering (DLS) and UV-Vis spectroscopy of a continuous flow during the CNT sonication dispersion process. This system can provide real-time monitoring of the quality of the suspension during the dispersion process and the stability of the suspension at post-dispersion stage. Monitoring the actual particle-size distribution can help determine the effective dispersion time and post-dispersion shelf life for potential use in process control and optimizing for scale-up manufacturing processes. We studied different CNT suspension systems, including MWNTs, SWNTs, graphene nanoplates, and their mixtures. For longer MWNTs with smaller diameters, the dispersion process achieved a steady agglomerate size around 100 nm with 40 minutes of sonication; for shorter and larger diameter MWNTs, due to their more packed agglomerate density, it took 60 minutes of sonication to reach the 100 nm agglomerate size. At the post-dispersion stage, the stability of CNT suspension showed nonlinear behavior due to the thermodynamic activity of CNT agglomerates. Under refrigerated storage condition, the increase of agglomerate size was reduced and the process of the CNT re-aggregation was prolonged by more than five times of the shelf life compared to the samples stored under room temperature. The study of dispersion of the carbon nanomaterial mixtures showed that MWNTs had helped the dispersion of SWNTs and graphene nanoplates throughout the sonication process to achieve a smaller agglomerate size after 75 minutes sonication. Quantitative quality baselines of the individual nanomaterials were established and used for controlling and optimizing the dispersion process and evaluating suspension stability. The dispersion mechanisms of different materials can be compared through the monitoring system.
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Date Issued: 2016
Identifier: FSU_2016SU_Yang_fsu_0071E_13331
Format: Thesis

Title: Nanocarbon Foam/Polymer Composite.
Creator: Jamal, Muhamad Shahrizan, Zhang, Mei, Okoli, Okenwa, Shrivastava, Abhishek Kumar, Florida State University, College of Engineering, Department of Industrial and Manufacturing...
Show moreJamal, Muhamad Shahrizan, Zhang, Mei, Okoli, Okenwa, Shrivastava, Abhishek Kumar, Florida State University, College of Engineering, Department of Industrial and Manufacturing Engineering
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Abstract/Description: Weight of a material and the system formed by such material is a critical factor for many applications. Traditionally, engineering designed porous structures, typically honeycomb structures, have been utilized for weight critical applications. The goal of this thesis work is to utilize the material with the lightest weight to fabricate a new type of foam that is not only lightweight and strong, but also electrically as well as thermally conductive and with tunable elasticity. A carbon...
Show moreWeight of a material and the system formed by such material is a critical factor for many applications. Traditionally, engineering designed porous structures, typically honeycomb structures, have been utilized for weight critical applications. The goal of this thesis work is to utilize the material with the lightest weight to fabricate a new type of foam that is not only lightweight and strong, but also electrically as well as thermally conductive and with tunable elasticity. A carbon nanotube (CNT) based nanocarbon foam was fabricated by using poly (methyl methacrylate) spheres as a template to create engineered pores. The junctions between the CNTs are secured using nanocarbon via the oxidation and carbonization of polyacrylonitrile. The resulting low density foam exhibits robustness in structure, high elasticity, thermal stability, corrosion resistance and is also electrically as well as thermally conductive. The strength of the foam is further boosted with the infiltration of PMMA polymer. The resulting composite foam is still porous and has higher mechanical strength. The electrical conductivity of the composite foam is not affected despite the presence of PMMA.
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Date Issued: 2016
Identifier: FSU_2016SU_Jamal_fsu_0071N_13228
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

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