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Zhang, Xiefei. "Studies on Single Wall Carbon Nanotube and Polymer Composite Films and Fibers." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/7610.
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Single wall carbon nanotubes (SWNT) have been extensively studied over the last decade due to their excellent comprehensive properties for a variety of applications. This study is focused on the applications of SWNTs as reinforcement for polymer matrices. Due to van der Waal interactions, SWNTs form bundles of about 30 nm diameters. In order to take full advantage of the SWNT mechanical properties, SWNT must exfoliate or at least disperse in small diameter bundle size. Optical microscopy and SEM only give qualitative information of dispersion. Quantitative characterization through TEM or AFM can be time consuming in order to get statistical result. In this study, simple method is developed to quantitatively estimate the size of SWNT bundle in dispersion based on the geometry controlled electrical percolation behavior. The SWNTs can be dispersed /exfoliated via PVP wrapped SWNT aqueous dispersion assisted by surfactants such as sodium dodycel sulfate. PVA / SWNT composite films prepared through PVP wrapped SWNTs exhibit improved mechanical properties as well as the evidence of load transfer from the polymer matrix to the SWNT as monitored by the Raman spectroscopy. SWNT can also be well dispersed into PVA/DMSO/H2O solution. Gel spinning of PVA/SWNT composite fiber has been successfully carried out with improved mechanical properties. Functionalized tubes can be used to enhance SWNT dispersion and exfoliation. Oxidation in strong acids is one method used for functionalizing nanotubes. SWNTs have been functionalized in nitric acid. The structure and properties of films (buckypaper) processed from nitric acid functionalized tubes have been studied exhibiting high tensile strength and high electrical conductivity. Nitric acid treatment results in selective degradation of the small diameter tubes.
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Soroudi, Azadeh. "Melt Spun Electro-Conductive Polymer Composite Fibers." Doctoral thesis, Högskolan i Borås, Institutionen Ingenjörshögskolan, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-3590.
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One interesting approach is the development of conductive polymer composite fibers for innovative textile applications such as in sensors, actuators and electrostatic discharge. In this study, conductive polymer composite fibers were prepared using several different blends containing conductive components: a conjugated polymer (polyaniline-complex) and/or carbon nanotubes. Different factors such as processing parameters, the morphology of the initial blends and the final fibers, fiber draw ratio and material selection were studied separately to characterize their effects on the fiber properties. In binary blends of PP/polyaniline-complex, the processing conditions, the matrix viscosity and the fiber draw ratio had substantial effects on the electrical conductivity of the fibers and linearity of resistance-voltage dependence. These factors were associated with each other to create conductive pathways through maintaining an appropriate balance of fibril formation and breakage along the fiber. The blend morphology was defined as the initial size of the dispersed conductive phase (polyaniline-phase), which depended on the melt blending conditions as well as the PP matrix viscosity. Depending on the initial droplet phase size, an optimum draw ratio was necessary to obtain maximum conductivity by promoting fibril formation (sufficient stress) and preventing fibril breakage (no excess stress) to create continuous pathways of conductive phase. Ternary blend fibers of PP/PA6/polyaniline-complex illustrated at least three-phase morphology with matrix/core-shell dispersed phase style. When ternary fibers were compared to binary fibers, the former could combine better mechanical and electrical properties only at a specific draw ratio; this showed that draw ratio was a more determinant factor for the ternary fibers, as both conductivity and tensile strength depended on the formation of fibrils from the core-shell droplets of the PA6/polyaniline-complex through the polypropylene matrix. The achieved maximum conductivity so far was in the range of 10 S/cm to 10 S/cm, which for different samples were observed at different fiber draw ratios depending on the mixing conditions, the matrix viscosity or whether the fiber was a binary or ternary blend. To improve the properties, PP/polyaniline-complex blends were filled with CNTs. The CNTs and the polyaniline-complex both had an increasing effect on the crystallization temperature and the thermal stability of PP. Furthermore, the maximum conductivity was observed in samples containing both CNTs and polyaniline-complex rather than the PP with either one of the fillers. Although increasing the content of CNTs improved the conductivity in PP/CNT fibers, the ease of melt spinning, diameter uniformity and mechanical properties of fibers were adversely affected. Diameter variation of PP/CNT as-spun fibers was shown to be an indication of hidden melt-drawings that had occurred during the fiber extrusion; this could lead to variations in morphology such as increases in the insulating microcracks and the distance between the conductive agglomerates in the drawn parts of the fiber. Variations in morphology result in variations in the electrical conductivity; consequently, the conductivity of such inhomogeneous fiber is no longer its physical property, as this varies with varying size.Thesis to be defended in public on Friday, May 20, 2011 at 10.00 at KC-salen, Kemigården 4, Göteborg, for the degree of Doctor of Philosophy.
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Lyons, Kevin Mark. "Tensile testing and stabilization/carbonization studies of polyacrylonitrile/carbon nanotube composite fibers." Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/45915.
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This study focuses on the processing, structure and properties of polyacrylonitrile (PAN)/ carbon nanotube (CNT) composite carbon fibers. Small diameter PAN/CNT based carbon fibers have been processed using sheath-core and islands-in-a-sea (INS) fiber spinning technology. These methods resulted in carbon fibers with diameters of ~3.5 μm and ~1 μm (for sheath-core and INS respectively). Poly (methyl methacrylate) has been used as the sheath or the sea component, which has been removed prior to carbonization. These fibers have been stabilized and carbonized using a batch process. The effect of stabilization has been characterized by Fourier Transform Infrared Spectroscopy (FTIR), wide-angle X-ray diffraction (WAXD), and differential scanning calorimetry (DSC). A non-isothermal extent of cyclization (Mcyc) from the DSC kinetics study was developed in order to obtain an unbiased method for determining the optimal stabilization condition. The results of Mcyc were found to be in good agreement with the experimental FTIR and WAXD observations. The carbon fiber fracture surfaces have been examined using SEM. Various test parameters that affect the tensile properties of the precursor fiber (both PAN and PAN/CNT), as well as carbon fiber have been studied. In an attempt to validate single filament tests, fiber tow testing has also been done using standard test methods. Batch processed carbon fibers obtained via sheath-core geometry exhibited tensile strengths as high as 6.5 GPa, while fibers processed by islands-in-a-sea geometry exhibited strength values as high as 7.7 GPa.
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Chae, Han Gi. "Polyacrylonitrile/carbon nanotube composite fibers." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/28125.
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Thesis (M. S.)--Polymer, Textile and Fiber Engineering, Georgia Institute of Technology, 2008.Committee Chair: Satish Kumar; Committee Member: Anselm Griffin; Committee Member: Dong Yao; Committee Member: Naresh Thadhani; Committee Member: Samuel Graham
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Choi, Young Ho. "Polyacrylonitrile / carbon nanotube composite fibers: effect of various processing parameters on fiber structure and properties." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/42902.
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This study elucidates the effect of various processing parameters on polyacrylonitrile (PAN) /carbon nanotube (CNT) composite fiber structure and properties. Interaction between PAN and MWNT enabled the gel-spun PAN/MWNT composite fiber to be drawn to a higher draw ratio, than the control PAN fiber, resulting in the composite fiber tensile strength value as high as 1.3 GPa. PAN/MWNT composite fibers were stabilized and carbonized, and the resulting fibers have been characterized for their structure and properties. The effect of precursor fiber shelf-time on the mechanical properties of the gel-spun PAN/MWNT composite fibers is also reported. A rheological study of PAN-co-MAA/few wall nanotube (FWNT) composite solution has been conducted. At low shear rates, the network of FWNTs contributes to elastic response, resulting in higher viscosity and storage modulus for the composite solution as compared to the control solution. On the other hand, at high shear rates, the network of FWNTs can be broken, resulting in lower viscosity for the composite solution than that for the control solution. Larger PAN crystal size (~16.2 nm) and enhanced mechanical properties are observed when the fiber was drawn at room temperature (cold-drawing) prior to being drawn at elevated temperature (~ 165 °C; hot-drawing). Azimuthal scan of wide angle X-ray diffraction (WAXD) and Raman G-band intensities were used for the evaluation of Herman's orientation factor for PAN crystal (fPAN) and FWNT (fFWNT), respectively. Significantly higher nanotube orientation was observed than PAN orientation at an early stage of fiber processing (i.e during spinning, cold-drawing). Differential scanning calorimetry (DSC) revealed that PAN-co-MAA fiber can be converted into cyclic structure at milder conditions than those for PAN. Continuous in-line stabilization, carbonization, and characterization of the resulting carbon fibers were carried out. Rheological and fiber spinning studies have also been carried out on PAN-co-MAA/VGCNF (vapor grown carbon nano fiber). The diameter of PAN-co-MAA/VGCNF composite fiber is smaller than that of the PAN-co-MAA control fiber with same draw ratio due to the suppressed die-swell in the presence of VGCNF. The mechanical properties of PAN-co-MAA control and PAN-co-MAA/VGCNF composite fibers were characterized. Crystalline structure and morphology of the solution-spun PAN-co-MAA/VGCNF fibers are characterized using WAXD and scanning electron microscopy (SEM), respectively. The volume fraction of PAN-CNT interphase in PAN matrix has been calculated to illustrate the impact of CNTs on structural change in PAN matrix, when ordered PAN molecules are developed in the vicinity of CNTs during fiber processing. The effect of PAN-CNT interphase thickness, CNT diameter, and mass density of CNT on volume fraction of PAN-CNT interphase has been explored.
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Jain, Rahul. "Carbon nanotube reinforced polyacrylonitrile and poly(etherketone) fibers." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/28257.
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Thesis (M. S.)--Polymer, Textile and Fiber Engineering, Georgia Institute of Technology, 2009.Committee Chair: Kumar, Satish; Committee Member: Bucknall, David; Committee Member: Griffin, Anselm; Committee Member: Shofner, Meisha; Committee Member: Yushin, Gleb
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Liu, Yaodong. "Stabilization and carbonization studies of polyacrylonitrile /carbon nanotube composite fibers." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/42933.
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Carbon fibers contain more than 90 wt. % carbon. They have low density, high specific strength and modulus, and good temperature and chemical resistance. Therefore, they are important candidate as reinforcement materials. Carbon fiber is made by pyrolysing precursor polymers. Polyacrylonitrile (PAN) which has been used as precursor to produce high strength carbon fiber is used as precursor in this study. The theoretical tensile strength of carbon fibers can reach over 100 GPa. Currently, the best commercial carbon fibers reach only 7.5 GPa. To make good quality carbon fiber and to narrow the gap between theoretical values and currently achieved experimental properties, the entire manufacturing process including fiber spinning, stabilization and carbonization, needs to be improved optimized. In this dissertation, the stabilization processes of gel-spun PAN/carbon nanotubes (CNTs) composite fibers are studied.
PAN/CNT (1 wt. % CNT) composite fibers are spun by dry-jet gel-spinning. Three types of CNTs with different number of walls and varying catalyst content are used as additives. The effect of different types of CNTs on the properties of the stabilized fibers was compared. It is found that the CNTs with the highest surface area shows the best reinforcement efficiency on the tensile modulus, and reduces the formation of β-amino nitrile. The residual catalyst in the range of 1 to 4 wt. % shows little effect on the mechanical properties of the stabilized fibers.
Stabilization involves complex chemical reactions, including cyclization, oxidation, dehydration, and cross-linking. These complex reactions are separated by using different gas environments during stabilization. The cross-linking reaction has the highest activation energy among all stabilization reactions, and requires a temperature higher than 300 DegC to be completed. The effect of applied tension on the stabilized fiber properties are investigated, and it is found that higher tension leads to better properties for the stabilized fiber, including higher Young's modulus, higher orientation, less formation of β-amino nitrile, and less shrinkage.
The relationship between stabilization conditions and the mechanical properties of the carbonized fiber is investigated, and the methods to identify optimum stabilization conditions are proposed. It is observed that the highest tension should be applied during both stabilization and carbonization, and the mechanical properties of the resulting carbon fibers are increased if fibers are further stabilized at a temperature of ~ 320 DegC to improve the cross-linking degree as compared with the fibers only stabilized at 255 DegC. The optimum stabilization time depends on both the stabilization temperature and on the applied tension. A new characterization method by monitoring the dynamic mechanical properties, while stabilization is in progress is used to narrow down the range of the optimum stabilization time. Also, the effect of carbonization temperature on the ultimate carbon fiber properties is studied in the batch process carbonization. Preliminary studies are carried out to find the relationship between the structure and properties of precursor fibers and the tensile strength of carbon fibers, including mechanical properties and co-monomers of precursor fibers.
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Liang, Jianghong. "Single Wall Carbon Nanotube/Polyacrylonitrile Composite Fiber." Thesis, Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/7613.
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Single Wall Carbon Nanotubes (SWNTs), discovered in 1993, have good mechanical, electrical and thermal properties. Polyacrylonitrile (PAN) is an important fiber for textiles as well as a precursor for carbon fibers. PAN has been produced since 1930s.
In this study, we have processed SWNT/PAN fibers by dry-jet wet spinning. Purified SWNT, nitric acid treated SWNTs, and benzonitrile functionalized SWNTs have been used. Fiber processing was done in Dimethyl Formamide (DMF) and coagulation was done in DMF/water mixture. The coagulated fibers were drawn (draw ratio of 6) at 95 oC.
Structure, orientation, and mechanical properties of these fibers have been studied. The cross-sections for all the fibers are not circular. Incorporation of SWNT in PAN results in improved mechanical properties, tensile modulus increased from 7.9 GPa for control PAN to 13.7 GPa for SWNT/PAN composite fiber, and functionalized SWNTs result in higher improvements with tensile modulus reaching 17.8 GPa for acid treated SWNT/PAN composite fibers. The theoretical analysis suggests that observed moduli of the composite fibers are consistent with the predicted values.
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Eyre, Kyle J. "Moisture absorption and stiffness degradation of carbon fiber reinforced polymer composite specimens exposed to accelerated environmental aging conditions." Laramie, Wyo. : University of Wyoming, 2007. http://proquest.umi.com/pqdweb?did=1313919681&sid=1&Fmt=2&clientId=18949&RQT=309&VName=PQD.
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Mottaghitalab, Vahid. "Development and characterisation of polyaniline-carbon nanotube conducting composite fibres." Access electronically, 2006. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20060731.095628/index.html.
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LUPONE, FEDERICO. "Additive manufacturing of carbon fiber reinforced thermoplastic polymer composites." Doctoral thesis, Politecnico di Torino, 2022. http://hdl.handle.net/11583/2966347.
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Breña, Sergio F. "Strengthening reinforced concrete bridges using carbon fiber reinforced polymer composites /." Full text (PDF) from UMI/Dissertation Abstracts International, 2000. http://wwwlib.umi.com/cr/utexas/fullcit?p3004223.
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Salama, Adel. "Laser machining of carbon fibre reinforced polymer composite." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/laser-machining-of-carbon-fibre-reinforced-polymer-composite(7310ed95-b876-480b-a8b4-2033b4309cb6).html.
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Carbon fibre reinforced polymer (CFRP) composites have found a wide range of applications in the aerospace, marine, sports and automotive industries owing to their lightweight and acceptable mechanical properties compared to the commonly used metallic materials. The currently dominating method of machining CFRP is by mechanical means that has found many problems including extensive tool wear, fibre pull-out and delamination. Lasers as non-contact tools have been widely applied for cutting and drilling materials. However, machining of CFRP composites using lasers can be challenging due to inhomogeneity in the material properties and structures, which can lead to thermal damage such as charring, heat affected zones (HAZs), resin recession and delamination. In previous studies, Nd:YAG, diode pumped solid state (DPSS), CO2 (continuous wave), disk and fibre lasers were used in machining CFRP composites and the control of damage such as the size of heat affected zones (HAZ) and achieving comparable material removal rate with the mechanical processes remain a challenge. Most reported work showed a typical heat affected zone of 0.2-1.2 mm. The availability of short pulsed transversely excited atmospheric (TEA) CO2 lasers and ultra-short laser pulse sources such as picosecond lasers make it possible to improve the laser machining quality of CFRP materials. In this research, the machining of CFRP composites using a microsecond pulsed TEA CO2 laser, a state of the art high power picosecond laser and a 1 kW single mode fibre laser system was investigated. The yielded heat affected zone was less than < 25 µm for the TEA CO2 and the picosecond laser machining, although the material removal rate was low. Additionally, it has been shown that the pulsed fibre laser improved the machining quality compared to that with the continuous mode. A potential application of the fibre laser for composite repair and remanufacturing was investigated. The interactions between picosecond laser beam and CFRP composite were studied in more detail including understanding the self-limiting effect in single and multiple parallel tracks drilling/machining through both experimental and theoretical studies. Furthermore, a sequential laser and mechanical drilling of CFRP was investigated to improve the machining rate. The work performed in this PhD was driven by aerospace industry needs, with the collaboration of Rolls-Royce plc and BAE Systems as industrial partners.
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Kim, Kun San. "Adhesion of graphite fibers to polycarbonate matrix : the role of fiber surface treatment." Thesis, Georgia Institute of Technology, 1987. http://hdl.handle.net/1853/8569.
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Sellitti, Claudio. "Surface characterization of carbon fibers and interfacial phenomena in carbon reinforced composites." Case Western Reserve University School of Graduate Studies / OhioLINK, 1990. http://rave.ohiolink.edu/etdc/view?acc_num=case1054570728.
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Negarestani, Reza. "Laser cutting of carbon fibre-reinforced polymer composite materials." Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/laser-cutting-of-carbon-fibrereinforced-polymer-composite-materials(90c7dab8-2b05-4098-aee7-d90a66b9face).html.
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Carbon fibre-reinforced polymer (CFRP) composite materials are in increasingly high demand, particularly in aerospace and automotive industries for reduced fuel consumption. This is due to their superior structural characteristics (both in fatigue and static conditions) and light weight. Anisotropic and heterogeneous features of these materials, however, have posed serious challenges in machining of CFRPs. Hence new machining technologies need to be investigated. Laser is a non-contact (eliminating toolwear) thermal process. Therefore, the thermal properties of the material are of crucial importance. Especially for composite materials which consist of different constituent materials. In CFRPs, carbon fibres are excellent conductors of heat (thermal conductivity of 50 W/(m.K)) while the polymer matrix is poor conductor (thermal conductivity of 0.1-0.3 W/(m.K)). This significant difference that can be similarly traced for other thermal properties such as heat of vaporisation and specific heat capacity are the source of defects in laser cutting of CFRP composites. Major quality challenges in laser cutting of these materials are delamination and matrix recession. Various laser systems and cutting techniques are investigated in this work to minimise these defects. Multiple-pass cutting using a high beam quality continuous wave (CW) mode fibre laser is found to be effective to minimise delamination at low power level and high scanning speeds. Multiple-pass cutting using nanosecond pulsed DPSS Nd:YAG laser is shown to reduce matrix recession. A novel technique using mixing of reactive and inert gases is introduced and demonstrated to minimise the matrix recession. In order to improve the quality and dimensional accuracy of CFRP laser machining, it is important to understand the mechanism of transient thermal behaviour and its effect on material removal. A three-dimensional model to simulate the transient temperature field and subsequent material removal is developed, for the first time, on a heterogeneous fibre-matrix mesh. In addition to the transient temperature field, the model also predicts the dimensions of the matrix recession during the laser machining process.
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Yang, Xiong. "Use of Fiber Reinforced Polymer Composite Cable for Post-tensioning Application." FIU Digital Commons, 2015. http://digitalcommons.fiu.edu/etd/2259.
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Corrosion of steel tendons is a major problem for post-tensioned concrete, especially because corrosion of the steel strands is often hard to detect inside grouted ducts. Non-metallic tendons can serve as an alternative material to steel for post-tensioning applications. Carbon fiber reinforced polymer (CFRP), given its higher strength and elastic modulus, as well as excellent durability and fatigue strength, is the most practical option for post-tensioning applications.
The primary objective of this research project was to assess the feasibility of the use of innovative carbon fiber reinforced polymer (CFRP) tendons and to develop guidelines for CFRP in post-tensioned bridge applications, including segmental bridges and pier caps.
An experimental investigation and a numerical simulation were conducted to compare the performance of a scaled segmental bridge model, post-tensioned with two types of carbon fiber strands and steel strands. The model was tested at different prestress levels and at different loading configurations. While the study confirms feasibility of both types of carbon fiber strands for segmental bridge applications, and their similar serviceability behavior, strands with higher elastic modulus could improve structural performance and minimize displacements beyond service loads.
As the second component of the project, a side-by-side comparison of two types of carbon fiber strands against steel strands was conducted in a scaled pier cap model. Two different strand arrangements were used for post-tensioning, with eight and six strands, respectively representing an over-design and a slight under-design relative to the factored demand. The model was tested under service and factored loads. The investigation confirmed the feasibility of using carbon fiber strands in unbonded post-tensioning of pier caps. Considering both serviceability and overload conditions, the general performance of the pier cap model was deemed acceptable using either type of carbon fiber strands and quite comparable to that of steel strands.
In another component of this research, creep stress tests were conducted with carbon fiber composite cable (CFCC). The anchorages for all the specimens were prepared using a commercially available expansive grout. Specimens withstood 95% of the guaranteed capacity provided by the manufacturer for a period of five months, without any sign of rupture.
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Lutz, Vincent. "Carbon nanotubes as nanofillers or fibers for multifunctional epoxy-based composites." Thesis, Lyon, INSA, 2014. http://www.theses.fr/2014ISAL0039.
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L’utilisation de composites à matrice thermodurcissable et fibres continues est en constante progression dans le secteur aéronautique, ferroviaire, et automobile. Afin d’améliorer les composites obtenus, notamment leur résistance à l’impact et leur conductivité électrique, des nanocharges organiques ou inorganiques peuvent être ajoutées. Les nanotubes de carbone (CNT) font partie des candidats les plus prometteurs pour le renforcement de composites à multi-échelle. Cependant, il s’avère difficile de contrôler la dispersion, la répartition et l’orientation des CNT, après les avoir mélangés aux prépolymères. Une nouvelle stratégie d’insertion des CNT dans un composite consiste à combiner des fibres de CNT avec des fibres de carbone. L’orientation et l’organisation structurelle des CNT au sein de la fibre permettent d’obtenir d’excellentes propriétés mécaniques et électriques. Dans notre étude, les propriétés de fibres contenant exclusivement des CNT, obtenues par direct spinning, ont été comparées à celles de fibres de carbone (non-ensimées, ensimées, et CNT en surface). Différentes interfaces entre les fibres de CNT, fibres de carbone et deux types de matrices époxy (de TG très différentes) ont été générées et testées par des essais de fragmentation de fibre dans la matrice. La contrainte de cisaillement interfaciale fibre/matrice a été évaluée afin de déterminer l’influence des diverses fibres et ensimages sur les performances mécaniques de composites à matrice organique et à fibres continues. En outre, la nature de l’adhésion et la qualité de l’interphase entre la matrice et la fibre ont été caractérisées par plusieurs techniques d’analyses et d’observations à multi-échellesNowadays, polymer-matrix composites reinforced with carbon fibers are increasingly used in the whole transport sector (aerospace, automotive and railway industries). However, the obtained parts still suffer from low impact resistance and low damage tolerance. To improve these properties, the matrix precursors have to be combined with organic or inorganic compounds to lead to multi-phased matrices. Among them, carbon nanotubes (CNT) are especially promising for targeting multi-scale reinforcement. Since high quality of the parts are required, continuous-fibers-reinforced composites can be produced by resin transfer molding (RTM) which also offers a reduced cost if compared with high temperature- and high pressure-based processes. However, RTM requires a very low viscosity of the polymer precursors and CNT-filled precursors are far too viscous to be injected on dry performs. In addition, this strategy does not allow for a control of the CNT location and orientation in the final part. In this study, innovative ways have been developed to insert CNT in the preform with local positioning and defined orientation. Deliveries of CNT in the matrix, from a neat carbon multi-nanotubes fiber produced by direct spinning, or from a CNT grown on carbon fiber were investigated in two types of epoxy matrices (with very different TG). Different polymer matrix/fiber interfaces have been generated using neat carbon multi-nanotubes fiber, CNT grown on carbon fiber and conventional carbon fiber, with or without sizing. A fine mechanical characterization of various fibers and particularly the measurement of single fiber interfacial properties have been performed in order to determine mechanical performance of continuous fiber reinforced composites. In addition, the nature of adhesion and quality of matrix/fiber interface have been fully evaluated by different multi-scale analyses and suitable microstructural observations
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Shukla, Jay G. "Effect of processing parameters on morphology and mechanical properties of carbon/PEEK (APC2) composite." Thesis, Georgia Institute of Technology, 1988. http://hdl.handle.net/1853/8276.
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Spencer, Ryan J. "Porosity Evaluation in Carbon Fiber Polymer Laminates using Acoustography." OpenSIUC, 2017. https://opensiuc.lib.siu.edu/theses/2148.
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In this research, through-transmission ultrasonic (TTU) Acoustography was applied to measure and quantify porosity levels in carbon fiber reinforced polymer (CFRP) composite laminates. This study employed several CFRP specimens with wide ranges of porosity prepared by altering the curing pressure during the manufacturing process. The Acoustography method, operating at 5 MHz, was able to show contrast in ultrasonic images obtained for composite laminates with varied porosity levels. Porosity levels in composite laminates were quantified using destructive methods: acid digestion and microscopy. Also, strength analysis tests were conducted to investigate the effect porosity has on the laminate’s structural integrity. From the results obtained, it was demonstrated that the mechanical properties, interlaminar shear strength (ILSS), and flexural strength of CFRP decreased with the increasing void content. In addition, Acoustography absorption coefficient measurements were related to varied porosity levels in the composite laminates. As the porosity content increased within the laminates, the acoustic absorption coefficient increased. These findings are significant because Acoustography is being developed as a faster alternative to traditional ultrasonic inspection of composites and porosity is an important anomaly to quantify utilizing NDE methods.
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Ventura, Cervellón Alejandra Marcela. "Sustainable polymer-tribology : Developing novel multiscale thermoplastic composites using recycled high-performance fibers." Thesis, Luleå tekniska universitet, Maskinelement, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-86910.
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The transition to a Circular Economy scheme that enables a more efficient usage of the resources is one of the most pressing needs in our society. From the industrial perspective this has been translated into new design philosophies and the search for more efficient systems. Polymeric composites have played a key role in the development of lighter components with good mechanical and tribological properties. Specifically, the demand of Carbon Fiber Reinforced Polymers (CFRP) has had an increasing trend since 1970s-1980s, becoming one of the kind of composites with the highest demand in the market to supply industries such as aerospace, automotive, construction, renewable energies, among others. With the increasing demand of CFRP materials some of the main challenges that arise are their disposal, environmental impact and cost of production to maintain the required supply. The use of Carbon Fibers as a reinforcement for polymeric matrices has been widely documented over the last decades, however the characterization of recycled Carbon Fibers for tribological applications is still scarce. Therefore, this investigation is focused on the mechanical and tribological characterization under water lubricated conditions of Ultra High Molecular Weight Polyethylene (UHMWPE) composites reinforced with virgin and recycled Carbon Fibers and Graphene Oxide. The findings of this work provide an important panorama regarding the performance of recycled Carbon Fibers, showing that they can have a comparable performance in mechanical properties and tribological behavior. This enables the use of recycled Carbon Fibers without compromising performance while reducing the environmental impact and cost.
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Pandolfi, Carlo. "Experimental characterization of carbon-fiber-reinforced polymer laminates." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/9777/.
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The goal of this thesis is to make static tensile test on four Carbon Fiber Reinforced Polymer laminates, in such a way as to obtain the ultimate tensile strength of these laminates; in particular, the laminates analyzed were produced by Hand Lay-up technology. Testing these laminates we have a reference point on which to compare other laminates and in particular CFRP laminate produced by RTM technology.
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Deng, Jiangang. "Durability of carbon fiber reinforced polymer (CFRP) repair/strengthening concrete beams." Laramie, Wyo. : University of Wyoming, 2008. http://proquest.umi.com/pqdweb?did=1663060011&sid=2&Fmt=2&clientId=18949&RQT=309&VName=PQD.
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Curnutt, Austin. "Research on the mechanics of CFRP composite lap joints." Thesis, Kansas State University, 2017. http://hdl.handle.net/2097/38191.
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Master of ScienceDepartment of Architectural Engineering
Donald J. Phillippi
For this thesis, research was performed on CFRP bonded composite lap-joints with one and two continuous laminas through the lap. Composite wraps used to retrofit existing structures use lap joints to maintain their integrity. The use of composites for retrofitting structures has many advantages over traditional methods, such as steel jacketing, and is becoming more widely accepted in the structural engineering industry. While much literature exists documenting the performance of composite wraps as a whole when applied to concrete columns, less information is available on the behavior of the lap-joint of the wrap. Developing a better understanding of how the lap-joint behaves will help researchers further understand composite column wraps. This research sought to determine what affect continuous middle laminas may have on the stiffness of lap joints and whether or not stress concentrations exist in the lap-joint due to a change in stiffness.
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FARINA, LUIS C. "Caracterizacao viscoelastica por meio de ensaios de fluencia e ruptura por fluencia de compositos polimericos de matriz de resina epoxidica e fibra de carbono." reponame:Repositório Institucional do IPEN, 2009. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9391.
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Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Flynn, Dara S. "Mechanical Behavior Analysis of a Carbon-Carbon Composite for Use in a Polymer Electrolyte Fuel Cell." Digital WPI, 2004. https://digitalcommons.wpi.edu/etd-theses/172.
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While there is a substantial amount of information regarding the electrochemical behavior of fuel cells and there components little to no information is available regarding the mechanical properties of fuel cell materials in stack setups. This set of experiments was set up to test mechanical properties of gas diffusion layer and bipolar plate materials in a one cell setup. Samples were clamped to specified pressures and deformation properties were observed and measured. Measurements were taken of impingements of the gas diffusion layers into the gas flow channels. A limit for compression of cell configurations was found to be approximately 300psi. Upon reaching the compression limit bipolar plates collapse and materials between plates show signs of breakage. Under compression diffusion media showed impingement into the gas flow channels as well as substantial compression of the three layer stack.
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Škriniarová, Nina. "Mechanická odezva dlouhými vlákny vyztuženého polymerního kompozitu." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2014. http://www.nusl.cz/ntk/nusl-217024.
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This diploma thesis is focused on monitoring of mechanical response of long-fiber reinforced polymer composite. Main part of this thesis was preparation of long-fiber reinforced composite specimens, on which matrix was reinforced by commercially sized glass fibers. For comparison of properties were prepared specimens reinforced by unsized glass fibers. Apart from preparing specimens reinforced by long glass fibers were prepared specimens contains long carbon fibers. For evaluation of mechanical response of the prepared composite specimen were used flexural test and short beam shear test. Mechanical response was evaluated with universal testing machine ZWICK Z010 and data were processed in OriginPro 8 program. Thanks to evaluation of the mechanical response of the prepared specimens was assessed adhesion to fiber-matrix interface. By examining the mechanical response or adhesion can be assessed efficiency of commercial fiber surface treatment and so standardize measurement to compare other options of surface treatments.
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Shalaby, Ashraf Mounir Mahmoud. "Development of a new spun concrete pole reinforced with carbon fiber reinforced polymer bars." Birmingham, Ala. : University of Alabama at Birmingham, 2007. https://www.mhsl.uab.edu/dt/2009r/shalaby.pdf.
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Thesis (Ph. D.)--University of Alabama at Birmingham, 2007.Title from PDF title page (viewed Feb. 5, 2010). Additional advisors: Ashraf Al Hamdan, Wilbur A. Hitchcock, Jason T. Kirby, Talat Salama. Includes bibliographical references (p. 148-153).
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Olka, Michael. "FLEXURAL MECHANICAL DURABILITY OF CONCRETE BEAMS STRENGTHENED BY EXTERNALLY BONDED CARBON FIBER REINFORCED POLYMER SHEETS." Master's thesis, University of Central Florida, 2009. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3120.
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About 77,600 bridges throughout the United States in the Federal Highway Association (FHWA) bridge database are listed as structurally deficient. This has created a need to either replace or strengthen bridges quickly and efficiently. Due to high costs for total replacement of deficient bridges, strengthening of existing bridges is a more economical alternative. A technique that has been developing over the past two decades is the strengthening of bridges using carbon fiber reinforced polymer (CFRP) sheets. The CFRP sheets are attached to the bottom of the bridge girders using structural adhesives so that the CFRP becomes an integral part of the bridge and carries a portion of the flexural loading. The CFRP sheets allow for an increase in the capacity of the bridge with minimal increase in the weight of the structure due to CFRP having a low density. Because the CFRP is expected to be an integral component and carry some of the long-term loading it is important to understand the long-term durability of the composite section. This thesis is part of a larger project, in which the long-term durability of the CFRP composite on concrete beams is investigated experimentally. The CFRP strengthened beams are exposed to fatigue testing and thermal-humidity cycling followed by failure testing. The testing scheme for this experiment allows for the investigation of the individual effects of fatigue and thermal-humidity loading as well as to explore the effects from combined fatigue and thermal-humidity loading. The investigation of the combined effects is a unique aspect of this experiment that has not been performed in prior studies. Results indicate that a polyurethane-based adhesive could provide a more durable bond for the CFRP-concrete interface than possible with epoxy-based adhesives.M.S.
Department of Civil and Environmental Engineering
Engineering and Computer Science
Civil Engineering MS
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Russell, Blair Edward. "Material Characterization and Life Prediction of a Carbon Fiber/Thermoplastic Matrix Composite for Use in Non-Bonded Flexible Risers." Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/30797.
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In the effort to improve oil production riser performance, new materials are being studied. In the present case, a Polymer Matrix Composite (PMC) is being considered as a replacement for carbon steel in flexible risers manufactured by Wellstream Inc., Panama City, Florida. The Materials Response Group (MRG) at Virginia Tech had the primary responsibility to develop the models for long-term behavior, especially remaining strength and life. The MRG is also responsible for the characterization of the material system with a focus on the effects of time, temperature, and environmental exposure. The present work is part of this effort. The motivation to use a composite material in a non-bonded flexible riser for use in the offshore oil industry is put forth. The requirements for such a material are detailed. Strength analysis and modeling methods are presented with experimental data. The effect of matrix crystallinity on composite mechanical properties is shown. A new method for investigating matrix behavior at elevated temperatures developed. A remaining strength life prediction methodology is recalled and applied to the case of combined fatigue and rupture loading.Master of Science
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Ghazali, Habibah. "Dual-Capsule Based Self-Healing of Epoxy and Carbon-Epoxy Laminated Composite." Thesis, The University of Sydney, 2016. http://hdl.handle.net/2123/15387.
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Since the year 2000, researchers have made extensive efforts to develop novel materials with self-healing ability by embedment of microencapsulated self-healing agents. The motivation behind these studies is to heal the crack once it occurs and to slow down crack growth in the materials. These materials were designed with the capability of repairing damage/fracture autonomously whenever it happens, and the materials subsequently recover their original properties. Many of the early-developed healing systems focused on the healing of polymers and their fibre-reinforced composites with a room temperature-curing system. Because of the difficulty in applying resins with microcapsules normally around 100 μm in size to reinforcing fibres during the fabrication process of composites and due to the limited space between the plies, most studies have adopted a low fibre volume fraction for ease of processing and fabrication. The realisation to structural composites containing a high fibre volume fraction was less studied. In general, a high fibre volume fraction is a critical factor for achieving high specific strength and high specific modulus of the resultant composites. Firstly, this study aims to develop a diglycidyl ether of bisphenol A (DGEBA) epoxy as the self-healing agent and characterise its capability in healing the elevated temperature-cured epoxy, epoxy-based adhesive joints, and carbon-fibre reinforced epoxy composites. A dual-capsule self-healing system containing DGEBA epoxy and mercaptan as its hardener, microencapsulated in similar sizes, was developed to be embedded into the base epoxy resin. This healing system was chosen to match that of the matrix of composite laminates fabricated in this study for its superior thermal stability. Although the DGEBA epoxy/mercaptan self-healing system has been reported to provide the epoxy with room temperature healing, the high viscosity imposed by the healing agent has made room temperature healing conditions less reliable for healing of composite laminates of a high fibre volume fraction, where the amount of the embedded microcapsules is constrained by fibres. Therefore, the effect of healing temperature on viscosity and healing efficiency in the base epoxy is studied to obtain the improved healing conditions. It was found that the better healing performance for this healing system is achieved at 70°C since the viscosity of DGEBA epoxy is much lower at this temperature. With a better flow behaviour, the healing agent has a better capacity to flow and spread onto crack surfaces. Apart from that it was also found that the formed healant film covering thin cavity between two crack surfaces is critical for the healing performance, and at the elevated temperature of 70°C, the full recovery in fracture toughness (KIC) is achieved for Mode I fracture in the epoxy. The dual-capsule self-healing system was then extended to heal delamination in carbon fibre (CF)/epoxy (EP) composite laminates after Mode I interlaminar fracture. One of the main focuses of this study is centred on CF/EP composite laminates embedded with the dual-capsule and with a high fibre volume fraction fabricated using the vacuum assisted resin infusion technique, with the aims to effectively heal delamination as well as matrix microcracking once they occur. Here, it was demonstrated that by properly modulating the amount of microcapsules dispersed on reinforcing CF fabrics, CF/EP composite laminates with a fibre volume fraction as high as 65% can be achieved. The self-healing performance after Mode I delamination in CF/EP composite laminates with the dual-capsule self-healing system of two different sizes (average 123 µm and 65 µm, respectively) of microcapsules was investigated. Effects of incorporating microcapsules on baseline properties of the composite laminates were investigated, and it was found that such incorporation first leads to some reduction in the baseline properties of the laminates. The CF/EP laminate with large size (123 µm) microcapsules shows 4.6% reduction in the original Mode I interlaminar fracture toughness (GIC) as compared to that of the base laminate; while the CF/EP laminate with small size (65 µm) microcapsules shows a reduction of 36.9%. Healing efficiency is characterised by the recovery in the Mode I critical stress intensity factor (KIC) measured using width-tapered double cantilever beam (WTDCB) specimens. Although the full recovery was achieved for the base laminate injected with the same healing agent, the healing efficiency with only 54% recovery was achieved for the laminate with the small size microcapsules, with the maximum being 57% in some cases. In the case of large size microcapsules, the healing efficiency increased to 69% recovery with the maximum being 80% in some cases. It was also observed that the recovery in Mode I interlaminar fracture toughness was directly correlated with the amount of healant film covering the fracture surfaces, with the highest healing efficiency obtained for the laminate with the largest film. In the following study, the self-healing performance after Mode II delamination in CF/EP laminates containing the dual-capsule self-healing system was investigated. The effect of incorporation of the microcapsules on Mode II interlaminar fracture toughness (GIIC) of CF/EP laminates was characterised using end-notched flexure (ENF) specimens. In contrast to the Mode I delamination tests, the results indicated that the Mode II interlaminar fracture toughness (GIIC) of the base CF/EP laminate was improved (up to 48%) with the incorporation of the dual-capsule self-healing system. When healed at 70°C, the dual-capsule self-healing system also provided the laminate with healing capability on Mode II delamination with 63% recovery in GIIC. Observation on the fracture surfaces also revealed that the healing efficiency varies directly with the concentration of healant and the healing of interlaminar region after Mode II fracture. Finally, the self-healing epoxy adhesive was developed using this dual-capsule self-healing system. The healing system was incorporated into a commercial two-part room temperature-cured epoxy adhesive. The addition of 3 wt% microcapsules in concentration into adhesive of 172 (± 50) μm in thickness was shown to increase the baseline lap-shear strength by 28%. The results also revealed an increment to the baseline fracture toughness (GIC) of the epoxy adhesive, with improvement as high as 80% for adhesive with thickness of 273 (±66) μm, measured using tapered-double cantilever beam (TDCB) specimens. The increase in fracture toughness was mainly attributed to enhanced plastic deformation of the host adhesive as well as the crack path deflection caused by the poor adhesion between the microcapsules and the epoxy adhesive. The healing efficiency based on the recovery in the original crack initiation and crack propagation fracture toughness is 52% and 74% respectively.
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Masghouni, Nejib. "Hybrid Carbon Fiber/ZnO Nanowires Polymeric Composite for Stuctural and Energy Harvesting Applications." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/64354.
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Despite the many attractive features of carbon fiber reinforced polymers (FRPs) composites, they are prone to failure due to delamination. The ability to tailor the fiber/matrix interface FRPs is crucial to the development of composite materials with enhanced structural performance. In this dissertation, ZnO nanowires (NWs) were grown on the surface of carbon fibers utilizing low temperature hydrothermal synthesis technique prior to the hybrid composite fabrication. The scanning electron microscopy revealed that the ZnO nanowires were grown uniformly on the surface of the carbon fabric. The surface grown ZnO NWs functionally-graded the composite material properties and ensured effective load transfer across the interface. To assess the influence of the ZnO NWs growth, reference samples were also prepared by exposing the carbon fabric to the hydrothermal conditions. The damping properties of the hybrid ZnO NWs-CFRP composite were examined using the dynamic mechanical analysis (DMA) technique. The results showed enhanced energy dissipation within the hybrid composite. Quasi-static tensile testing revealed that the in-plane and out-of-plane strengths and moduli of the hybrid FRP composite were also boosted.
The interlaminar shear strength (ILSS) measurements suggested the improvement in the mechanical properties of the composite to the enhanced adhesion between the ZnO nanowires and the other constituents (carbon fiber and epoxy). It was necessary thus, to utilize the molecular dynamics simulations (MD) to investigate the adhesion within the CFRP structure upon growing the ZnO nanowires on the surface of the carbon fibers. Molecular models of the carbon fibers, the epoxy matrix and the ZnO nanowires were built. The resulting molecular structures were minimized and placed within a simulation box with periodic boundary conditions. The MD simulations were performed using the force field COMPASS to account for the empirical energy interactions between the different toms in the simulation box. Proper statistical thermodynamics were employed to relate the dynamics of the molecular model to the macroscale thermodynamic states (pressure, temperature and volume). Per the computed potential energies of the different components of the composite, it was found that the polar surfaces in the ZnO structures facilitates good adhesion properties in the graphite-epoxy composite.
Besides the attractive mechanical properties of the ZnO nanowires, their piezoelectric and semiconductor properties were sought to design an energy harvesting device. To ensure sufficient charges collection from the mechanically stressed individual ZnO nanowires, a copper layer was sputtered on top of the ZnO nanowires which introduced also a Schottky effect. The mechanical excitation was provided by exposing the device to different vibration environment. The output voltage and currents were measured at the conditions (in terms of frequency and resistive load). It was demonstrated that the electrical output could be enhanced by stacking up similar devices in series or in parallel.
Finally, in an attempt to exploit the reversibility of the electromechanical coupling of the energy harvesting device, the constitutive properties of the hybrid ZnO nanowires-CFRP composite were estimated using the Mori-Tanaka approach. This approach was validated by a finite element model (FEM). The FEM simulations were performed on a representative volume element (RVE) to reduce the computational time. The results demonstrated that the mechanical properties of the hybrid ZnO NWs-CFRP composite were better than those for the baseline CFRP composite with identical carbon fiber volume fraction (but with no ZnO NWs) which confirmed the experimental findings. Furthermore, the electro-elastic properties of the hybrid composite were determined by applying proper boundary conditions to the FE RVE.
The work outlined in this dissertation will enable significant advancement in the next generation of hybrid composites with improved structural and energy harvesting multifunctionalties.Ph. D.
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LEBRAO, GUILHERME W. "Processamento e caracterização de material compósito polimérico obtido com nanotubo de carbono funcionalizado." reponame:Repositório Institucional do IPEN, 2013. http://repositorio.ipen.br:8080/xmlui/handle/123456789/23595.
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Tese (Doutorado em Tecnologia Nuclear)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Kadam, Ruthvik Dinesh. "Design and Additive Manufacturing of Carbon-Fiber Reinforced Polymer Microlattice with High Stiffness and High Damping." Thesis, Virginia Tech, 2019. http://hdl.handle.net/10919/103009.
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Carbon fiber reinforced polymer (CFRP) composites are known for their high stiffness-to-weight and high strength-to-weight ratios and hence are of great interest in several engineering fields such as aerospace, automotive and defense. However, despite their light weight, high stiffness and high strength, their application in these fields is limited due to their poor energy dissipation and vibration damping capabilities. This thesis presents a two-phase microlattice design to overcome this problem. To realize this design, a novel tape casting integrated multi-material stereolithography system is developed and mechanical properties of samples fabricated using this system are evaluated. The design incorporating a stiff phase (CFRP) and a high loss phase, exhibiting high stiffness as well as high damping, is studied via analytical and experimental approaches. To investigate its damping performance, mechanical properties at small-strain and large-strain regimes are measured through dynamic material analysis (DMA) and quasi-static cyclic compression tests respectively. It is seen that both intrinsic (small-strain) and structural (large-strain) damping in terms of a figure of merit (FOM), E1/3tanδ/ρ, can be enhanced by a small addition of a high loss phase in Reuss configuration. Moreover, it is seen that structural damping is improved at low relative densities due to the presence of elastic buckling during deformation. For design usefulness, tunability maps, displaying FOM in terms of design parameters, are developed by curve fitting of experimental measurements. The microlattice design is also evaluated quantitatively by comparing it with existing families of materials in a stiffness-loss map, which shows that the design is as stiff as commercial CFRP composites and as dissipative as elastomers.Master of Science
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Cormier, Daniel. "Repair of Conductive Layer on Carbon Fibre Reinforced Polymer Composite with Cold Gas Dynamic Spray." Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/33160.
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Carbon fibre reinforced composites are known for their high specific strength-to-weight ratio and are of great interest to the aerospace industry. Incorporating these materials into the fuselage, like in Boeing's 787 "Dreamliner", offers considerable weight reduction which increases flying efficiency, and reduces the cost of flying.
In flight, aircraft are often subject to lightning strikes which, in the case of composites, can result in localized melting given the high resistive nature of the material. Aerospace carbon fibre composites often incorporate a metallic mesh or foil within the composite layers to dissipate the electrical charge through the large aircraft. The damage to the aircraft is minimized but not always eliminated. This research aims to elaborate a practical technique to deposit thin layers of conductive material on the surface of aerospace grade composites. Using Cold Gas Dynamic Spray (CGDS), such coatings could be used to repair damaged components.
An experimental research approach was used to develop metallic coated composites. Using the CGDS equipment of Centerline (SST-P), specific parameters (such as gas temperature and stagnation pressure) were determined for each type of metallic coating (tin-based & copper-based). The use of bond coats was explored in order to attain the desired coatings. Once optimized, these coatings were evaluated with respect to their corrosive, adhesive, and electrical properties following industry standards.
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Chan, Kathleen Joyce. "Investigation of Processing Conditions and Viscoelastic Properties on Frictional Sliding Behavior of Unidirectional Carbon Fiber Epoxy Prepreg." Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/86444.
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The quality of continuous fiber reinforced polymer matrix composite parts and structures depends strongly on the friction during the composite forming process. The two major types of friction that cause deformations during this process are ply-ply friction and tool-ply friction. One of the challenges in the composite forming process is the occurrence of wrinkling and shape distortion of the fabric caused by the surface differences between the forming tool and surface of the laminate. Frictional measurements of composites can vary widely depending on processing parameters, measurement technique, and instruments used.
In this study, a commercial rheometer was used to evaluate tool-ply friction of unidirectional carbon fiber epoxy prepreg at various contact pressures, temperatures and sliding velocities. Viscoelastic properties such as the complex viscosity (η*), storage modulus (G'), loss modulus (G"), and loss factor (tan δ) were used to determine the critical transition events (such as gelation) during cure. An understanding of changes in viscoelastic properties as a function of time, temperature, and cure provides insight for establishing a suitable processing range for compression forming of prepreg systems.
Surface imaging results were coupled with rheological results to qualitatively examine the effects of processing parameters on prepreg distortions. Changes in gap height over the measurement interval qualitatively describe the changes in contact area and contact mechanisms between the tool-ply surfaces. The results indicate that friction behavior of the prepreg system is a contribution of adhesive and frictional forces, where increase in viscosity, reduction in gap height, and cure of the sample correlate to higher friction values.Master of Science
The quality of composite parts and structures depends strongly on the friction present during the composite forming process. One of the major challenges in the forming process is the occurrence of wrinkling and shape distortions of the fabric caused by the surface differences between the forming tool and material. The presence of these defects can compromise the final material property and lead to failure when in use. Frictional measurements of composites can vary widely depending on processing parameters, measurement technique, and instruments used. The extent of interaction between the tool and surface of the material depends on the tooling height, and by extension, contact area, which cannot easily be monitored with traditional test designs. A commercial rheometer was used in this study to evaluate tool-ply friction of unidirectional carbon fiber epoxy prepreg at various contact pressures, temperatures, and sliding velocities. Gap height and torque were monitored to provide information on the frictional dependence of processing parameters. In addition, surface-imaging results were coupled with rheological results to examine the relationship between friction and fiber distortions. The understanding of changes in material property with respect to the tooling process is the key to optimizing the composite forming process.
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Dawood, Mina Magdy Riad. "Fundamental Behavior of Steel-Concrete Composite Beams Strengthened with High Modulus Carbon Fiber Reinforced Polymer (CFRP) Materials." NCSU, 2005. http://www.lib.ncsu.edu/theses/available/etd-06292005-192140/.
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There is a growing need for a cost-effective, durable repair system that can be used for the repair and strengthening of steel bridges. Recently, high modulus carbon fiber reinforced polymers (CFRP) have been developed with a modulus of elasticity approximately two times greater than that of steel. Externally bonded high modulus CFRP materials have successfully been used to increase the elastic stiffness and ultimate capacity of steel-concrete composite beams However, since the technology is relatively new, the detailed behavior of steel bridge members strengthened with high modulus CFRP is not yet well understood. The current research investigates three aspects of the behavior of steel-concrete composite beams in detail. An experimental program was conducted to investigate the behavior of steel-concrete composite beams strengthened with high modulus CFRP materials. In the first phase of the study the behavior under overloading conditions was investigated. In the second phase of the research, the fatigue durability of the system was examined. In the third phase, the possible presence of shear-lag between the steel beam and the CFRP materials was investigated in detail. An analytical model was developed which can be used to determine the ultimate capacity and elastic stiffness increase for steel beams strengthened with high modulus CFRP materials. Additionally, a set of criteria are proposed which can be used to determine the allowable increase in the live load level for steel beams strengthened with high modulus CFRP materials.
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Kohlman, Lee W. "Evaluation of Test Methods for Triaxial Braid Composites and the Development of a Large Multiaxial Test Frame for Validation Using Braided Tube Specimens." University of Akron / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=akron1333047848.
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Lee, Tuan Kuan 1976. "Shear strength of reinforced concrete T-beams strengthened using carbon fibre reinforced polymer (CFRP) laminates." Monash University, Dept. of Civil Engineering, 2003. http://arrow.monash.edu.au/hdl/1959.1/6647.
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Ye, Sheng Yin. "Valorisation de déchets composites à matrices polymériques renforcées de fibres de carbone par un procédé de vapo-thermolyse." Phd thesis, Toulouse, INPT, 2012. http://oatao.univ-toulouse.fr/16132/1/ye_partie_1_sur_3.pdf.
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Le composite à matrices polymériques renforcées de fibres de carbone (CFRP) est un matériau précieux en raison de ses excellentes propriétés mécaniques, légèreté et durabilité. Un gain important d’efficacité et une réduction des émissions de carbone peuvent être obtenus en remplaçant les pièces métalliques par les CFRPs dans l'industrie du transport. Toutefois, le recyclage de déchets CFRP est problématique, car le renfort de fibres de carbone est chimiquement lié à la matrice de résine réticulée. Néanmoins, la réutilisation de fibres de carbone couteuses rend le recyclage des CFRPs potentiellement viable en termes d’économie. Dans notre laboratoire, une étude multi-échelle d’un procédé de vapo-thermolyse a été réalisée, dont l'objectif est de séparer les fibres de carbone de matrices polymériques en utilisant la vapeur d’eau surchauffée. Afin d’obtenir une meilleure compréhension du comportement de dégradation thermique des matériaux CFRP, de nombreuses analyses thermiques ainsi que les caractérisations physico-chimiques ont été effectuées sur différentes fibres de carbone, résines polymériques (époxyde ou polyphénylène sulfide) et les composites correspondants. Une étude cinétique a été également abordée. Les plans d’expériences réalisées à l'échelle pilote dans un réacteur sophistiqué permettent de déterminer les conditions expérimentales optimales du procédé semi-industriel. Les fibres de carbone récupérées à partir de conditions optimisées apparaissent propres, sans résine et conservent plus de 90% de leur résistance à la traction d’origine. Les phases gazeuse et liquide émises ont également été quantitativement analysées. La modélisation de l’écoulement et des transferts thermiques du réacteur ainsi que la simulation de la dégradation de matrices polymériques montrent les résultats comparables avec les observations expérimentales. L’analyse du cycle de vie indique que le recyclage des CFRPs peut être favorable pour l’environnement par rapport au scénario de mise en décharge.
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Hart, Robert James. "Characterization of carbon fiber polymer matrix composites subjected to simultaneous application of electric current pulse and low velocity impact." Thesis, University of Iowa, 2011. https://ir.uiowa.edu/etd/1143.
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The use of composite materials in aerospace, electronics, and wind industries has become increasingly common, and these composite components are required to carry mechanical, electrical, and thermal loads simultaneously. A unique property of carbon fiber composites is that when an electric current is applied to the specimen, the mechanical strength of the specimen increases. Previous studies have shown that the higher the electric current, the greater the increase in impact strength. However, as current passes through the composite, heat is generated through Joule heating. This Joule heating can cause degradation of the composite and thus a loss in strength. In order to minimize the negative effects of heating, it is desired to apply a very high current for a very short duration of time. This thesis investigated the material responses of carbon fiber composite plates subjected to electrical current pulse loads of up to 1700 Amps. For 32 ply unidirectional IM7/977-3 specimens, the peak impact load and absorbed energy increased slightly with the addition of a current pulse at the time of an impact event. In 16 ply cross-ply IM7/977-2 specimens, the addition of the current pulse caused detrimental effects due to electrical arcing at the interface between the composite and electrodes. Further refinement of the experimental setup should minimize the risk of electrical arcing and should better elucidate the effects of a current pulse on the impact strength of the specimens.
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Motoc, Dana. "Development of green composites based on epoxidized vegetable oils (EVOs) with hybrid reinforcements: natural and inorganic fibers." Doctoral thesis, Universitat Politècnica de València, 2017. http://hdl.handle.net/10251/90399.
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The main aim of this work id to provide integral methods to predict and characterize the properties of composite structures based on hybrid polymers and reinforcements, that could lead to useful results from an industrial point of view. This is addressed, if possible, by theoretical predictions of the effective properties by using the available experimental data.
The first part is focused on the scientific achievements of the author that allowed a quantitative characterization of the main effective properties of several composite architectures from hybrid polymers and reinforcements, based on bio matrices, tailor-made matrices and different theoretical and simulation methods using computer software to allow good comparison. The second part defines the future research lines to continue this initial investigation.
The main objectives are clearly defined to give the reader a sound background with the appropriate concepts that are specifically discussed in the following chapters. As a main objective, this research work makes a first attempt to provide a systematic analysis and prediction of composite hybrid structures.El objetivo general del trabajo es proporcionar medios integrales para predecir y caracterizar las propiedades de las estructuras de compuestos basados en polímeros y refuerzos híbridos, principales que pueden producir resultados de utilidad práctica simultáneamente. Esto se logra comparando, siempre que sea posible, las predicciones teóricas de las propiedades efectivas con los datos experimentales disponibles. Una primera parte se ocupa de los logros científicos del autor que permitieron caracterizar cuantitativamente las principales propiedades efectivas de las arquitecturas de compuestos basados en polímeros y refuerzos híbridos, basados en matrices bio, auto-desarrollados y diferentes métodos teóricos y de simulación por ordenador utilizados para la comparación. La segunda parte identifica las orientaciones futuras para la evolución y desarrollo de la ciencia y la investigación. Los objetivos generales fueron subrayados y concisos para dar al lector una visión previa de los conceptos que serán discutidos específicamente en los siguientes capítulos. Indirectamente, apuntan hacia uno de los objetivos principales de este trabajo, a saber, proporcionar una dirección para el análisis sistemático de materiales compuestos a base de refuerzos híbridos.
L'objectiu general d'aquest treball es proporcionar els mitjos integrals per tal de predir i caracteritzar les propietats d'estructures de compòsits basats en polímers i reforçaments híbrids, que poden produir resultats amb utilitat pràctica simultàniament. Aquest objectiu s'aconsegueix comparant, sempre que és possible, les prediccions teòriques de les propietats efectives amb les dades experimentals disponibles. Una primera part es centra en els temes científics en què ha treballat l'autor que han permès caracteritzar quantitativament les principals propietats efectives de les arquitectures de compòsits basades en polímers i reforçaments híbrids, derivats de matrius bio, auto-desenvolupats i diferents mètodes teòrics i de simulació informàtica per a una correcta comparació. La segona part identifica les orientacions futures per tal d'establir l'evolució i desenvolupament de la ciència i investigació lligada a la temàtica de la tesi. Els objectius generals han sigut clarament definits per tal de donar-li al lector una visió prèvia i sòlida dels conceptes que es discuteixen en capítols venidors. Indirectament, apunten cap a un dels objectius principals d'aquest treball, a saber, proporcionar una direcció per a l'anàlisi sistemàtica de materials compòsits a base de polímers i reforçaments híbrids.
Motoc, D. (2017). Development of green composites based on epoxidized vegetable oils (EVOs) with hybrid reinforcements: natural and inorganic fibers [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/90399
TESIS
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Assaf, Ihab Adeeb. "Shear strengthening of reinforced concrete beams using an external carbon fibre reinforced polymer (CFRP) composite of low elastic modulus." Thesis, University of Salford, 2007. http://usir.salford.ac.uk/26555/.
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Beam-column joints designed seismically are considered impractical due to the congestion of steel stirrups. Currently, CFRP is used for strengthening reinforced concrete structures that have reduced integrity due to corrosion of steel reinforcement or unintentional overloading. The aim of this thesis is to mitigate the congestion of steel stirrups in the beam-column joint regions using an externally bonded CFRP composite and to possibly propose initial 'new build' design rules. Experimental work was conducted on 24 reinforced concrete beams with different percentages of steel shear reinforcement and varying amounts of CFRP. Six of these were tested under cyclic load. Significant reduction was observed as the RC beams were subjected to load reversal significantly higher than their service load. 18 beams were tested under static load in order to find the contribution of the CFRP to the shear capacity with varying percentages of steel stirrups. The results show that the CFRP contribution to the shear capacity is significant at zero and low ratios and decreases with an increase in the percentage of steel stirrups. The CFRP contribution is reduced significantly at high percentages of steel stirrup as the mode of failure becomes flexural. For strengthened beams having no steel shear reinforcement, the CFRP contribution is evaluated using current design rules. Load sharing between the CFRP and steel stirrups was observed and this relationship is very important for development of the current design rules. An alteration in the mode failure for the strengthened beam having a moderate percentage of steel stirrups was observed and similar behaviour was noticed with the beam conventionally reinforced with high ratio of steel stirrups. This is very beneficial in practice where the congested steel causes problems. Finite element analyses were carried out using ANSYS to attempt to predict the behaviour of further beams, caveats for which are highlighted within the thesis. The results for load sharing between the CFRP and steel stirrups shows that the relationship between the CFRP contribution to the shear capacity and the percentage of steel stirrups is not proportional as observed experimentally. Future work recommends a repeat of the experimental test with more instrumentation. Experimental tests on more complex structures (i.e. beam-column joints) are recommended where the shear reinforcement and confinement could be provided through the CFRP and hence reduce the congestion of steel stirrups. Using other FE codes is also recommended with an increased budget.
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Eldo, Danny. "Improving Interfacial Fracture Resistance of Sandwich Composite Structures by PES/CNT Nanofibres Interleaving and Z-pinning." Thesis, The University of Sydney, 2017. http://hdl.handle.net/2123/17125.
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Sandwich structure is one type of composite materials that has been widely used in automotive, marine and aerospace structures. It offers high specific modulus and specific strength. Sandwich structures consist of two thin face plates that enclose a thick core. The face plate is generally stiff enough to resist bending load, whilst the foam core is of lower modulus, lightweight yet it can transfer the shear and compressive loadings. Sandwich structures with composite faces have been applied to fabricate aerospace structures (e.g., engine cowling, floor panels, etc.) because of their excellent bending stiffness and their resistance to impact (good energy absorption). However, sandwich composites commonly suffer face-core interface failure that could lead to catastrophic failure of the whole structure. This failure would also give a significant increase on its maintenance and repair cost. To alleviate the interface failure between face materials and core, there are several techniques that have been proposed: (a) through-thickness reinforcement by inserting z-pins to connect the faces and the core; (b) insertion of an interleaf (thin layer) which acts as an adhesive between the faces and the core; and (c) matrix modification utilizing polymer nanocomposites (or nanofillers) on the facing materials (which the modified matrix is able to penetrate into the top surface of the core material) to improve face/core interface bonding. The aim of this research is to investigate the improvement level of the face/core interface strength by z-pinning and interleaving. Here, the role of z-pins and interleaves with nanofillers in changing the delamination resistance under mode I (opening mode) was investigated by the double cantilever beam (DCB) test. The results showed improvement in both reinforcement methods on mode I debonding fracture toughness. Cracked sandwich beam (CSB) test was carried out to study the enhancement of fracture resistance of the face-core interface of the structure under mode II (shear loading mode). Almost similar to mode I test, mode II tests also showed a significant improvement in mode II fracture toughness up to 9.5 times in z-pinning. Unlike z-pinning, interleaving did not show a significant result with only 11% improvement at most. Particularly on z-pinning, the increased mode I fracture toughness was achieved by the role of z-pin bridging on crack growth whose effect is controlled by the crack-wake bridging law. Pullout tests were performed to study the bridging law due to the z-pins. The results showed that pullout was dominantly from the face laminates and that the interface bonding between the z-pin and the foam-core was very small and neglected in the analysis. Computer simulation of mode I DCB tests with z-pins was done to compare the model predictions with obtained experimental data.
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Tann, David Bohua. "Retrofitting of mechanically degraded concrete structures using fibre reinforced polymer composites." Thesis, University of South Wales, 2001. https://pure.southwales.ac.uk/en/studentthesis/retrofitting-of-mechanically-degraded-concrete-structures-using-fibre-reinforced-polymer-composites(efce1110-34e1-457d-8ec5-3ef5da026018).html.
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This research involves the study of the short term loaded behaviour of mechanically degraded reinforced concrete (RC) flexural elements, which are strengthened with fibre reinforced polymer (FRP) composites. The two main objectives have been: (a) to conduct a series of realistic tests, the results of which would be used to establish the design criteria, and (b) to carry out analytical modelling and hence develop a set of suitable design equations. It is expected that this work will contribute towards the establishment of definitive design guidelines for the strengthening of reinforced concrete structures using advanced fibre composites. The experimental study concentrated on the laboratory testing of 30 simply supported, and 4 two-span continuous full size RC beams, which were strengthened by either FRP plates or fabric sheets. The failure modes of these beams, at ultimate limit state, were examined and the influencing factors were identified. A premature and extremely brittle collapse mechanism was found to be the predominant type of failure for beams strengthened with a large area of FRP composites. A modified semi-empirical approach was presented for predicting the failure load of such over strengthened beams. Despite the lack of ductility in fibre composites, it was found that the FRP strengthened members would exhibit acceptable ductile characteristics, if they were designed to be under strengthened. A new design-based methodology for quantifying the deformability of FRP strengthened elements was proposed, and its difference to the conventional concept of ductility was discussed. The available techniques for ductility evaluation of FRP strengthened concrete members were reviewed and a suitable method was recommended for determining ductility level of FRP strengthened members. A non-linear material based analytical model was developed to simulate the flexural behaviour of the strengthened and control beams, the results were seen to match very well. The parametric study provided an insight into the effects of various factors including the mechanical properties and cross sectional area of FRP composites, on the failure modes and ductility characteristics of the strengthened beams. Based on the findings of the experimental and analytical studies, design equations in the BS 8110 format were developed, and design case studies have been carried out. It was concluded that fibre composites could effectively and safely strengthen mechanically degraded reinforced concrete structures if appropriately designed. The modes of failure and the degree of performance enhancement of FRP strengthened beams depend largely on the composite material properties as well as the original strength and stiffness of the RC structure. If the FRP strengthened elements were designed to be under-strengthened, then the premature and brittle failure mode could be prevented and ductile failure mode could be achieved. It was also found that existing steel reinforcement would always yield before the FRP composite reached the ultimate strength. Furthermore, a critical reinforcement ratio, above which FRP strengthening should not be carried out, was defined. It was concluded that FRP strengthening is most suitable for reinforced concrete floor slabs, bridge decks, flanged beams and other relatively lightly reinforced elements. The study also revealed that to avoid a brittle concrete failure, existing doubly reinforced members should not be strengthened by FRP composites.
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SILVA, NELSON M. da. "Obtencao e comportamento mecanodinamico de compositos com matriz polimerica reforcada com fibras de carbono." reponame:Repositório Institucional do IPEN, 2001. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10888.
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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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Nguyen, Thanh Hai. "Contribution à l'étude du comportement thermomécanique à très haute température des matériaux composites pour la réparation et/ou le renforcement des structures de Génie Civil." Thesis, Lyon 1, 2015. http://www.theses.fr/2015LYO10244/document.
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Dans le domaine du renforcement et/ou de la réparation des structures en béton armé par des matériaux composites à l'aide de la méthode du collage extérieur au moyen d'un adhésif époxy, une des préoccupations de la communauté scientifique est l'intégrité structurelle de ce système dans le cas d'incendie dans lequel la haute température est une caractéristique essentielle et peut atteindre jusqu'à 1200°C. Ce travail de recherche est axé sur le comportement thermomécanique à très haute température des matériaux composites [un composite à base de polymère carbone/ époxy (Carbon Fiber Reinforced Polymer- CFRP), un composite textile/ mortier cimentaire (Textile Reinforced Concrete- TRC) et un adhésif à base d'époxy]. L'évolution des propriétés mécaniques et d'autres aspects mécaniques de ces matériaux composites avec la température a été caractérisée. Une nouvelle procédure expérimentale concernant la mesure de la déformation de l'éprouvette à l'aide du capteur laser est développée et validée. Une étude numérique et expérimentale a été réalisée dans le but de déterminer principalement la température à la rupture des joints « composite/ adhésif/ composite » sous les sollicitations mécaniques et thermiques. L'efficacité de la protection thermique de deux isolants [PROMASPRAY®T (produit commercial de la société PROMAT] et Isolant A (produit développé par le LGCIE site Tusset) a aussi été étudiée dans cette thèse. Enfin, une approche numérique, à l'aide du logiciel ANSYS, est utilisée afin de déterminer, de façon préliminaire et approximative, à l'échelle matériau, les propriétés thermiques des matériaux (composite textile/ mortier cimentaire -TRC et Isolant A)In the area of the strengthening and/or the reparation of reinforced concrete structures with composites by means of the external bonding method using an epoxy adhesive, one of the preoccupation of the scientific community is the structural integrity of this system in the event of fire in which the high temperature is the essential feature et can reach up to 1200°C. This research focuses on the thermo-mechanical behavior of composite materials [carbon/epoxy adhesive composite (or carbon fiber reinforced polymer (CFRP), textile/cementitious mortar composite (or textile reinforced concrete (TRC)] and an epoxy-based adhesive. The evolution of mechanical properties and other mechanical aspects of these materials with the temperature has been characterized. A new experimental procedure concerning the measurement of sample strain by the laser sensor is developed and validated. An experimental and numerical study has been realized in order to mainly determine the temperature at the failure of "composite/adhesive/composite" joints under thermal and mechanical loadings. The effectiveness of the thermal protection of two insulators [PROMASPRAY®T (a commercial product of the PROMAT company and the insulator A (product developed by the LGCIE site Tuset)] has also been investigated in this PhD thesis. Finally, a numerical approach, using ANSYS software, is used to determine, in the preliminary and approximate way, at material scale, thermal properties of the materials [the textile reinforced concrete (TRC) and the insulator A]
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Jain, Ayush. "Development and Characterization of Multi-scale Polymer Composite Materials for Tribological Applications." Thesis, Luleå tekniska universitet, Maskinelement, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-65241.
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With industries aiming at higher efficiencies, lightweight parts, and easier manufacturability there has been a recent trend of replacing the metallic materials with polymeric materials and its composites. Particularly in the automotive industry, there is a demand of replacing metallic material of bushes and bearings with polymer based materials (PBM). For these heavy performance requirements (as in automobiles), the commonly used industrial polymers like Acetal and Nylon fail to provide good mechanical and tribological performance. High-performance polymer like Polyphenylene Sulfide (PPS) is a relatively newer material and shows a potential of being a PBM alternative for metallic bearings in automobiles if their tribological performance can be improved. One of the ways of improving the tribological performance of the polymer is by the addition of filler material, hence making a polymer composite. In this study, we used Short Carbon Fibre as micro-reinforcement material and Nano-diamonds and Graphene Oxide as nano-reinforcement material to make PPS composites. The varying mechanical and tribological behaviour of PPS composites with different weight percentage of reinforcement materials was investigated. The optimum composition of the reinforcement materials was identified, which resulted in significant improvement in mechanical and tribological properties of the base material.
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BEIM, KIRA F. "Estudo comparativo das tensões cisalhantes na interface entre camadas de um compósito polimérico de fibra de carbono pelos metodos numérico e experimental." reponame:Repositório Institucional do IPEN, 2008. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11599.
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Dissertação (Mestrado)
IPEN/D
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP
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Bettelli, Mercedes Amelia. "Effect of Induction-Heat Post-Curing on Residual Stresses in Fast-Curing Carbon Fibre Reinforced Composites." Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-80527.
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Manufacturing induced shape distortions is a common problem for composite materials. Due to the non-isotropic nature of carbon fibre reinforced polymers (CFRP) unavoidable deformations occur during part production. During fabrication of polymer composites, the material obtains its final shape at elevated temperatures. The curing process involves a transition from the liquid state to the solid, glassy state, allowing bonding between fibres and matrix. As the material cools the mismatch in thermal expansion coefficients and cure shrinkage obtained during the matrix polymerization leads to residual stresses on the mechanical level within composite part. There is a great interest from the aircraft and automotive industries, to increase the ability to understand development of shape distortions and residual stresses during the cure, since these deformations often lead to dissatisfaction of tolerances and it is essential to predict the deformations beforehand in order to compensate time and cost. In this context, a study of residual stresses during the curing process of thermosetting resin composites is presented. A methodology is proposed for predicting the formation and development of manufacturing- induced residual stresses. The present project reports on a comprehensive experimental study on the dependency of different short curing cycles on the build-up of residual stresses in a carbon fibre/fast-curing epoxy system and evaluate of post-curing methods through induction heating and oven post-curing with unidirectional [904] and unsymmetrical [9020] laminates. It includes characterization in thermo-elastic properties and degree-of-cure of the material by Thermal bending test, thermal expansion test, mechanical tensile test and Differential Scanning Calorimetry (DSC) in non-post-cured and post-cured laminates. The results showed slight variation in the thermal properties and not effect in the mechanical properties at different cure and post-curing conditions. Analytical data by Laminate Analysis program validated the experimental thermo-elastic data with analytical simulations. In addition, it is shown improvements in the temperature distributions in the post-curing by induction heating with different experimental set-ups, however, oven post-curing showed a more systematic system, higher heat efficient a low cure temperature, with more consistent mechanisms of shape distortions and residual stresses compared to induction heating. These findings are relevant for the future development of prediction methods for process induced deformations of Fast Curing Epoxy Resins (FCER).