This study focuses on the processing, structure, and properties of gel spun polyacrylonitrile (PAN) and polyacrylonitrile/carbon nanotube (PAN/CNT) carbon fibers. Gel spun PAN based carbon fibers are manufactured beginning with a study of PAN dissolution in an organic solvent (dimethylformamide, DMF). Homogeneity of the PAN/DMF solution is determined through dynamic shear rheology, and the slope of the Han Plot (log G’ vs log G’’). Solutions were then extruded into gel spun fibers using a 100 filament fiber spinning apparatus in a class 1000 cleanroom. Fibers were then subjected to fiber drawing, stabilization, and carbonization, to convert the PAN precursor fiber into carbon fiber. Carbon fiber tensile strength was shown to scale with the homogeneity of the PAN/DMF solution, as determined by the slope of the log G’ vs log G’’ plot. After the development of the understanding between the homogeneity of the PAN/DMF solutions on the gel spun PAN based carbon fiber tensile properties, the effect of altering the fiber spinning processing conditions on the gel spun PAN based carbon fiber structure and properties is pursued. Cross-sectional shape of the gel spun PAN precursor fiber, characterized with a stereomicroscope, was found to become more circular in cross-section as the gelation bath temperature was increased, the amount of solvent in the gelation bath was increased, and when the solvent was switched from DMF to dimethylacetamide (DMAc). Gel spun fibers were then subjected to fiber drawing, stabilization, and carbonization to manufacture the carbon fiber. Carbon fibers were characterized to determine single filament tensile properties and fiber structure using wide-angle x-ray diffraction (WAXD) and high resolution transmission electron microscopy (HRTEM). It was found that the carbon fiber tensile properties decreased as the carbon fiber circularity increased, as a result of the differences in microstructure of the carbon fiber that result from differences in fiber spinning conditions. In the second half of this study, the addition of CNT into the PAN precursor and carbon fiber is investigated. CNT addition occurs during the solution processing phase, prior to gel spinning. As a first study, Raman spectroscopy is employed to investigate the bundling behavior of the CNT after gel spinning and drawing of the PAN/CNT fibers. By monitoring the peak intensity of the (12,1) chirality in the as-received CNT powder, and in differently processed PAN/CNT fibers, the quality of CNT dispersion can be quickly monitored. PAN/CNT fibers were then subject to single filament straining, with Raman spectra collected as a function of PAN/CNT filament strain. As a result of the PAN/CNT strain, stress induced G’ Raman band shifts were observed in the CNT, indicating successful stress transfer from the surrounding PAN matrix to the dispersed CNT. Utilization of the shear lag theory allows for the calculation of the interfacial shear strength between the PAN and incorporated CNT, which is found to increase as the quality of CNT (higher aspect ratio, increased graphitic perfection, and reduced impurity content), quality of CNT dispersion, and fiber drawing increase. PAN/CNT fibers were then subjected to stabilization and carbonization for the manufacture of gel spun PAN/CNT based carbon fibers. These fibers were then characterized to investigate the effect of CNT incorporation on the structure and properties of the carbonized fibers. The gel spun PAN/CNT based carbon fibers were compared to commercially produced T300 (Toray) and IM7 (Hexcel) carbon fibers, and gel spun PAN based carbon fiber. Fiber structure was determined from WAXD and HRTEM. Carbon fibers properties investigated include tensile properties, and electrical and thermal conductivity. PAN/CNT based carbon fibers exhibited a 103% increase in room temperature thermal conductivity as compared to commercially available IM7, and a 24% increase in electrical conductivity as compared to IM7. These studies provide a further understanding of the processing, structure, property relationships in PAN and PAN/CNT based carbon fibers, beginning at the solution processing phase. Through the manufacture of more homogeneous PAN/DMF solutions and investigations of the fiber spinning process, gel spun PAN based carbon fibers with a tensile strength and modulus of 5.8 GPa and 375 GPa, respectively, were successfully manufactured in a continuous carbonization facility. Gel spun PAN/CNT based carbon fibers exhibit room temperature electrical and thermal conductivities as high as 74.2 kS/m and 33.5 W/m-K.

The purpose of this thesis is to understand dynamic behaviors of carbon fiber composite golf shaft and the influence of different carbon fiber shaft flexes on club heads. To achieve the purpose, the researcher used the finite element method (FEM) software LS-DYNA and ANSYS to analyze the dynamic behaviors of carbon fiber composite golf shaft. He also applied three rigid bodies and two revote joint in a swing mode to simulate swing motion. In the same driving moment, the comparison provides golfer with a reference for selecting suitable carbon fiber composite golf shaft. It also offers other researchers an FEM model to do further analysis of dynamic behaviors of golf heads with the carbon fiber composite shaft.

Abstract The objectives of the thesis are to study and research the function of the fuel cell¡¦s bipolar plate which is vital to the Proton Exchange Membrane fuel cell¡Aand to create a new bipolar plate composed of nonhomogeneous plate and conductive object which conductive object are put through light weight plastic plate in consideration of low cost¡Bmini size¡Blight weight and high efficiency¡Atogether with a series of test for its capability. Of the same section area¡Athe electric resistance of carbon fiber used in this experiment is lower than traditional graphite bipolar plate.According to related literature¡Athe resistant of the graphite bipolar plateis lower than the ones made of other materials or composite material.The carbon fiber is a suitable conductive object for bipolar plate consequently. Without leakage¡Athe material are stand the differential pressure up to 0.5 kg/cm2 through the leakage/pressure tests.It is good enough in most of practical application.The strength of bipolar plate to resist the differential pressure is related to the plate strength and the strength of bond¡Ainterface between bond and plate or bond and carbon fiber.The proper bond is very important in this case. The efficiency of fuel cell decreases rapidly in line with the increase of loading during the efficiency test of fuel cell and sudden drop portion situates at Ohm resistance domain.Other papers describe about the main factor of Ohm resistance domain is resistance loss¡Aparameter include conductive coefficient¡Barea of conductive material¡Blength of conductive material.The most different of experiment compare with previous is the area of conductive material.Therefore the area of conductive fiber in bipolar plate influences the efficiency of fuel cell a lot. Through the research¡Athe availability of the new bipolar plate composed of nonhomogeneous plate and conductive object is proven and the cause of its defect in efficiency is identified for improvement in practical application.

A High electromagnetic shielding, light weight, low cost plastic package is developed by using a woven continuous carbon fiber (WCCF) epoxy composite. Three different weaving types of WCCF, plain¡Bbalanced twill and uni-direction structure, are fabricated for understanding the shielding property of the WCCF composites. By weaving the WCCF in a balanced twill structure with excellent conductive network, it shows that the SE can reach to about 80dB under plane-wave source measurement and about 50dB in the near-field source measurement. By comparison of cost, weight, and shielding performance for optical transceiver modules fabricated by the housings of woven continuous carbon fiber, nanoscale hollow carbon nanocapulses (HCNCs) epoxy composites and nylon and liquid crystal polymer (LCP) with carbon fiber filler composite, the WCCF composites shows lower cost, light weight, and higher electromagnetic shielding than the other types of composites.

This study combined photocatalytic technology with activated carbon adsorption to decompose gaseous pollutants. Gaseous pollutants were initially adsorbed and concentrated by activated carbon and could be further decomposed more effectively by photocatalytic technology. This study coated TiO2 on the activated carbon fiber (ACF) by a sol-gel process for conducting the adsorption and decomposition of acetone in a batch reactor. Operating parameters investigated in this study included the initial concentration of acetone (13.6 £gM and 27.2 £gM), reaction temperature (50¢J~70¢J), oxygen concentration (0.5%~20%), and water vapor (0 £gM~244.9 £gM). The incident UV light of 365 nm was irradiated by a 15-watt low-pressure mercury lamp placing above the photocatalytic batch reactor. The ACF coated with TiO2 was placed in the center of the reactor. Acetone was injected into the reactor to conduct photocatalytic tests. Reactants and products were analyzed quantitatively by a gas chromatography with electron capture detector (GC/ECD) and a flame ionization detector followed by a methaneizer (GC/FID-Methaneizer). Results from the photocatalysis tests indicated that, among the commercial TiO2 (Degussa P-25), NO3-/TiO2 and SO42-/TiO2, SO42-/TiO2 had the best photoactivity reduced acetone concentration and reaction time substantially. The end products was mainly CO2 and CO, which resulted in the mineralization ratio above 95%. Results from the operating parameter tests revealed that the increase of the initial acetone concentration enhanced the amount of acetone adsorbed on the ACF, which however did not increase the reaction rate of acetone. Although the increase of reaction temperature could reduce the amount of acetone adsorbed on the ACF, decomposition rate of acetone could be promoted, so as the yield rate and mineralization ratio of products (CO2 and CO). Increasing oxygen concentration did not influence the decomposition significantly except for oxygen concentration lower than 1%. The increase of water vapor would slightly decrease the amount of acetone adsorbed on the ACF, which did not decrease the decomposition of acetone anyway. This study revealed that the decomposition of acetone on TiO2/ACF can enhance the mass transfer of acetone substantially.

An effort concerned with the feasibility of achieving melt-processable polyacrylonitrile copolymer system precursors for producing high modulus carbon fibers is detailed. High molecular weight poly(acrylonitrile-ran-methyl acrylate) (PAN-MA) copolymer with high acrylonitrile content were mixed with various water containing binary melting point modifiers to produce systems that formed stable melts at temperatures below the temperature corresponding to the onset of PAN-MA crosslinking. The structure of the copolymer was found to be 96.5 ± 0.13 mole % acrylonitrile and 4.40 ± 0.13 mole % methyl acrylate by 1H-NMR with an Mw ]= 238 kDa and dispersity of 1.9 determined by size exclusion chromatography. A reduction in the Tm of the copolymer of 200 C was established for a copolymer/melting point modifier system containing copolymer mixed with water and acetonitrile with the following composition: PAN-MA/ACN/H2O 55/25/20 wt:wt:wt. This corresponds to the greatest reduction in a PAN-based copolymer melting temperature yet reported. From isothermal DSC and pressurized capillary rheometry experiments it was found that the stability of the resulting melts shows a strong temperature dependence, but does not show a strong dependence on shear rate. Copolymer mixtures with H2O and acetonitrile or H2O and adiponitrile were found to be suitable for melt-extrusion at 170 C with viscosities ranging from 1800-2000 Pa*s with stabilities greater than 1 hour. The modification of membranes to improve gas separation properties is of considerable interest. Crosslinking is one route to modify membranes, but the resulting effects on thin membranes have yet to be investigated to understand the impact of such modification at thicknesses that are relevant to industrial membranes. In this study, the influences of UV irradiation and physical aging on O2 and N2 gas permeation properties of thin (~ 150 nm) glassy poly(arylene ether ketone) (PAEK) films at 35 C and 2 atm were investigated. Thin PAEK films prepared from tetramethyl bisphenol A and 4,4'-difluorobenzophenone were UV irradiated on both sides in air or N2 at wavelengths of 254 nm or 365 nm. This induced crosslinking and, in some cases, photooxidation. Gas permeability decreased and O2/N2 selectivity increased as UV irradiation and aging time were increased. At 254 nm, samples irradiated in air had lower permeability coefficients and higher selectivities than samples irradiated in N2, and this was ascribed to additional decreases in free volume due to photooxidation in air-irradiated samples. Additionally, air-irradiated samples at 254 nm exhibited less physical aging than non-crosslinked and N2-irradiated samples at 254 nm, possibly due to interactions among photooxidative polar products that may restrict polymer chain mobility, thereby lowering the aging rate. The influence of water vapor on physical aging of air-irradiated samples was examined. Finally, irradiation at 254 nm leads to more extensive crosslinking and/or photooxidation than irradiation at 365 nm, possibly due to greater UV absorption by the polymer and the higher probability of radical formation at the lower wavelength. Poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) is utilized for gas separation membranes. It has a relatively high free volume with high gas permeabilities but suffers from low selectivities. PPO polymers with Mn's from 2000-22,000 g/mole were synthesized and blended with a poly(arylene ether ketone) derived from bisphenol A and difluorobenzophenone (BPA-PAEK). DSC showed that the blends with all but the lowest molecular weight PPO had two Tgs, thus suggesting that two phases were present. The ketone carbon and benzylic methyl groups on the BPA-PAEK and the PPO polymers crosslinked upon exposure to UV light. The gel fractions after UV exposure were high and the tensile properties were similar to the PPO control polymer that is currently used as a gas separation membrane. The crosslinked blends had improved gas selectivities over their linear counterparts. The 90/10 wt/wt 22k PPO/BPA PAEK crosslinked blends gained the most O2/N2 selectivity and maintained a high permeability. Two series of high molecular weight disulfonated poly(arylene ether sulfone) random copolymers were synthesized as proton exchange membranes for high temperature water electrolyzers. These copolymers differed based on the position of the ether bonds on the aromatic rings. One series was comprised of fully para-substituted hydroquinone comonomer and the other series incorporated 25 mole % of a meta-substituted comonomer, resorcinol, and 75 mole % hydroquinone. The influence of the substitution position on water uptake and electrochemical properties of the membranes were investigated and compared to the state-of-the-art membrane, Nafion. Mechanical properties of the membranes were measured for the first time in fully hydrated conditions at room and elevated temperatures. While submerged in water, these hydrocarbon-based copolymers had moduli an order of magnitude higher than Nafion membrane. Selected copolymers of each series showed dramatically increased proton conductivity at elevated temperature and fully hydrated conditions while their H2 gas permeabilities were well controlled over a wide range of temperatures. These improved properties were attributed to the high glass transition temperature of poly(arylene ether sulfone)s. / Ph. D.

Indiana University-Purdue University Indianapolis (IUPUI) / The use of carbon-fiber reinforced composite materials is not novel in the field of motorsports industry. Their use in collapsible structures for crashworthiness is however not fully understood and predicted. Due to the complex failure mechanisms occurring within the material, the energy absorbing capacity cannot be easily pre dicted. The need to understand their contributions in crashworthy structures is thus of great importance. Furthermore, failure of carbon-fiber composites is highly depen dent on the geometry of structure. Problems arise in both experimental and numerical modelling of these structures. Although many explicit FEA codes exist, they often include experimental parameters that need to be calibrated through either coupon tests or actual crash tests. As composite structures become more commonly used in automotive industry, it is necessary to set some guidelines to successfully model and simulate composite crashworthy structures. The numerical modelling was done in LS-DYNA Enhanced composite damage MAT54. The material properties were configured using experimental coupon tests. The tests were conducted on square composite tubes. The Specific Energy Absorption (SEA) of the tubes were calculated through several coupons. As SEA is a function of geometry, it was necessary to conduct tests with similar geometry as seen in nosecone. MAT54 was chosen to simulate both crush and crash simulations due to its capability to simulate element level crushing. Furthermore, various modifications within the material model, improve its accuracy to determine composite failure. The research utilizes the characterization of material inputs in MAT54 by con ducting quasi-static compression tests on simpler but similar geometry. By utilizing inputs, a zonal optimization was conducted on the nosecone geometry. The number of layers, layer orientations and ply thicknesses were varied to vary the energy absorbed per zone. The deceleration of the vehicle can thus be controlled, and the weight of the structure could be reduced.

Carbon nanotubes have now been a subject of intense research for approaching two decades. Although a short time relative to most conventional materials, much hype about the intrinsic properties of this material has now been substantiated by experiment. The results are conclusive that carbon nanotubes are truly phenomenal materials with highly desirable mechanical, electrical and thermal properties. Furthermore, multiwall carbon nanotubes (MWNTs) have emerged as the most economically viable and abundant form of carbon nanotubes, and therefore the most likely candidate for application. The key materials engineering challenge remains in effectively transferring their properties to macro-scale materials in the form of composites. It is here that research merges with application. This dissertation has therefore been directed to focus on carbon nanotube composites in an applied sense. Here, the state of the art is reviewed, and experimental results of carefully selected composite systems, studied in detail for (1) mechanical, (2) electrical and (3) thermal properties, are presented and discussed. In terms of mechanical properties, the effects of MWNTs for augmentation of the tensile properties of PAN-based carbon fiber, and fatigue performance of poly(methyl methacrylate) are investigated and reported. In MWNT composite PAN-based carbon fiber, the formation of an ordered interphase layer sheathing the nanotubes was observed in fracture surfaces, which indicated a clear importance of their function to template the growth of carbon formation in the PAN-based matrix fiber. These structures open up a route to nano-scale tailorability of the crystallographic morphology of the composite fibers. Large improvements in fatigue performance were observed in MWNT/PMMA composites compared to MWNT/chopped carbon fiber composites, and attributed to the nanometer scale dimensions of the MWNTs enabling them to mitigate submicron damage such as polymer crazing. In terms of electrical and thermal properties, MWNT/epoxy composites were superior to MWNT/carbon black composites. Furthermore, extremely large improvements in the thermal conductivity of epoxy were observed for epoxy-infiltrated aligned MWNT arrays. The alignment of the MWNTs was shown to play a dominant role in enabling the improvement. Finally, these results, in concert with the literature are discussed in terms of the application of carbon nanotubes in engineering materials.

This thesis presents a parametric study on the effects of how damage arrestment devices application interacts with a fastener in a composite sandwich panel. The primary objective of the damage arrestment device was to prevent the failure of the composite face sheet, such as crack propagation, around the hole/fastener joint. The damage arrestment devices are made of composite strips that are inserted under the face sheet to increase the overall structural strength of the panel and to prevent the propagation of failure along the hole. This was supposed to be a quicker and stronger alternative to potted inserts for composite sandwich panels for designer. The manufacturing curing cycle of the composite sandwich specimens has been carried out by using a Tetrahedron Composite Air Press. The press has been used to fabricate composite sandwich panels by applying constant pressure and variable heat to create panels with dimensions of 5” x 2” x .552”. The panels were stacked using a polyurethane foam, Last-A-Foam FR-6710 with two layers of a carbon-fiber/epoxy weave, LTM45, on both sides of the foam. The specimens were loaded under a compressive strain of 0.5 mm/min. The damage arrestment devices’ thickness was varied and tested under both monotonic and fatigue loading. The experimental results indicate that as the thickness of the device increased the overall strength of the part increased at a parabolic curve with it topping at a thickness of 0.065” and a strength increase of 109%. Under fatigue loading, a control group test case and damage arrestment device configuration case was tested. The experimental results indicate that both cases have similar fatigue trends but shows that the damage arrestment specimens are stronger due to the increase of structural strength. The experimental results were compared with numerical results or Finite Element Model. The results showed that numerical results can capture the linear or elastic portion of the experimental results having identical Elastic Modulus values. The models do differ in the maximum displacement of the specimen and the failure mode around the hole of the composite sandwich panel. The discrepancy in displacement and the failure mode was attributed to inaccurate loading on the hole of the composite sandwich panel and non-linear modeling of the solution. The correlation between the FEM and the experimental data was good enough in predicting the trends of the composite sandwich panels.

In this thesis, the treatments of MEA and the special structures within carbon fiber bunch unipolar plates on the performance of PEMFC are studied. At first, the factors affecting on the water content within MEA will be studied. A passive HFC stack usually exposes in the ambient no matter that it works or not. However, the ambient is far from saturated. The water within MEA will vaporize continuously. Especially, if the stack is shutdown for a long period, there is no water generation in the cathode and then the membrane will be short in water. If it occurs, the conductivity of H+ will decrease greatly, and the electrode of MEA is also possible to separate from its membrane. This separation will make the performance of the stack an unrecovered decay. On the other hand, in order to improve the performance of a air-breathing HFC, the inner structure within cathode carbon fiber bunch unipolar plates is modified. The structure of the unipolar plates is modified in the following three aspects: 1. Increasing soft end height of carbon fiber bunch, 2. Increasing the number of silver-coated wires in carbon fiber bunch, 3. Cutting several serrated slots on the soft end of carbon fiber bunch. In the MEA treatment, firstly, a MEA is boiled in 80oC, 0.5M H2SO4 solution and then boiled in 80oC DI water for an hour, respectively. When the single-cell HFC operates in hydrogen inlet pressure 0.1 bar, air-breathing, and room temperature, experimental results display that the power density of this HFC with the aforementioned treatments and the special structure of unipolar plates can reach a value about 185mW/cm2. This value is about 130% higher than that of the untreated MEA and about 50% higher than that of the treatment of MEA only immersed in DI water. In addition, the comparison of the performance of HFC between with carbon fiber bunch unipolar plates and with graphite unipolar plates are also studied. The experimental result displays that the performance of HFC with the carbon fiber bunch unipolar plates is superior to that with graphite unipolar plates, especially the fuel cell operating under low gas inlet pressure.