Dissertations / Theses on the topic 'Carbon Fiber Reinforced Composite'
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Pintossi, Marco. "Carbon fiber reinforced composite suspensions for a solar vehicle." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/20564/.
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Questa tesi si svolge nell’ambito di progettazione CAD e produzione di componenti per il settore dell’automotive in CFRP, in questo particolare caso, per un’auto elettrica a pannelli solari.
Il lavoro da me svolto, aperto con una panoramica generale sulle tecnologie a basse emissioni oggi disponibili, è stato fatto a seguito di un percorso personale divisibile in tre fasi principali iniziate nel 2018 con la collaborazione alla costruzione della vettura Emilia 4, con la quale l’Università ha preso parte all’ASC 2018, una gara tenutasi in America, che ci ha visti vincitori della categoria cruiser. Ed è proprio parlando di competizioni che entriamo nella seconda fase del mio percorso, che vede affiancarsi alla trasferta americana, la trasferta australiana del 2019 per competere nel BWSC.
La terza ed ultima fase di questo percorso, che temporalmente è avvenuta tra le due competizioni, è stata la progettazione di un componente di Emilia 4, i bracci delle sospensioni anteriori e posteriori, utilizzando la fibra di carbonio tramite la progettazione CAD 3D, sfruttando Ansys e Solidworks. Il lavoro di tesi si impegna quindi ad unire le competenze acquisite in aula con le nuove tecnologie nel campo dei materiali, usando come veicolo di comunicazione la programmazione CAD.
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Castro, Gabriel. "Drilling carbon fiber reinforced plastic and titanium stacks." Pullman, Wash. : Washington State University, 2010. http://www.dissertations.wsu.edu/Thesis/Spring2010/g_castro_042210.pdf.
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Thesis (M.S. in mechanical engineering)--Washington State University, May 2010.Title from PDF title page (viewed on July 16, 2010). "School of Engineering and Computer Science." Includes bibliographical references (p. 109-112).
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Brunnacker, Lena. "Short Carbon Fiber-Reinforced Thermoplastic Composites for Jet Engine Components." Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-76733.
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State-of-the-art aircraft engine manufactures aim to reduce theirenvironmental impact steadily. Thereby they attempt to increase engineefficiency, use new renewable fuel sources and most importantly aim toreduce component weight. While Titanium, Aluminum and continuousfiber reinforced thermosetting composites and superalloys prevail in thecurrent material selection, the present work desires to raise awareness fora novel group of materials; short carbon fiber reinforced thermoplasticcomposites (SCFRTPs). In this kind of composite short fibers givedimensional stability and strength while the thermoplastic matrix ensuresthe physical properties, even at temperatures up to 300°C.Even though in some applications these materials offer great potential tosave weight and cost, it is not clear if their properties suffice to be used indemanding areas of the aero engine and if they are still able provide costand weight reductions there.The present work therefore investigated potential aero-engine componentsthat could be replaced by SCFRTPs. With literature, manufacturer data andmaterial and process modelling approaches, it is shown that SCFRTPsmechanical and physical properties suffice for the selected component.Further it is shown that cost reductions up to 77% and weight savings upto 67% compared to the Ti-6Al-4V baseline component are possible.
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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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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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Hsieh, Feng-Hsu. "Nanofiber reinforced epoxy composite." Ohio : Ohio University, 2006. http://www.ohiolink.edu/etd/view.cgi?ohiou1146149557.
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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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Durkin, Craig Raymond. "Low-Cost Continuous Production of Carbon Fiber-Reinforced Aluminum Composites." Thesis, Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19857.
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The research conducted in this study was concerned with the development of low-cost continuous production of carbon fiber/aluminum composites. Two coatings, alumina and zirconia, were applied to the fibers to protect against interfacial degradation. They were applied using a sol-gel method and common metal salts. The fibers were infiltrated with molten aluminum using an ultrasound sonicator. The resultant composites were well-infiltrated and were tested in tension to determine their mechanical properties. Strengths were only 15-35% of the theoretical values predicted by the rule of mixtures. The composite microstructure revealed a sizable void fraction and that the fibers within the composites did not contain any coating on their surface. It was hypothesized that this was a result of few exposed graphite plane edges on the fiber surface, causing poor adhesion of the oxide coating to the fiber surface. To improve adhesion, an amorphous carbon coating was applied to the fiber surface, but still the oxide coatings were removed from the fibers upon infiltration. It was found, however, that the carbon coating on its own did strengthen the interface between the fiber and the aluminum.
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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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Ozcan, Soydan. "Microstructure-property-performance relationships of c-fiber-reinforced carbon composite friction materials /." Available to subscribers only, 2008. http://proquest.umi.com/pqdweb?did=1686179081&sid=4&Fmt=2&clientId=1509&RQT=309&VName=PQD.
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Thesis (Ph. D.)--Southern Illinois University Carbondale, 2008."Department of Engineering Science." Keywords: Carbon composite, Friction materials, Carbon-fiber reinforcement Includes bibliographical references (p. 106-115). Also available online.
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Sheats, Matthew Reed. "Rehabilitation of reinforced concrete pier caps using carbon fiber reinforced composites." Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/19490.
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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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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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Zanial, Muhammad Munir. "Effects of large damage on residual strength of carbon fiber reinforced composite laminates." Thesis, Wichita State University, 2014. http://hdl.handle.net/10057/10987.
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Tension or compression fracture behavior studies are normally initiated with open hole tension or compression tests performed at the laminate level. While these test data serve as an excellent starting point in residual strength studies in small notch sizes, the need to evaluate and verify the residual strength for larger structures and at larger notch sizes region is still there. An experimental study was performed with the focus on large notch sizes of circular hole and narrow slit flaw configurations on laminates fabricated with a carbon/epoxy oven-cure capable prepreg material system. The current part of the study focused on uniaxial tension loading with a constant width and height to flaw dimension ratio. Experimental test data were then combined with lamina and laminate level data for residual strength curves generation and the curves were validated against Whitney-Nuismer and Mar-Lin fracture mechanics models. The effects of flaw sizes and the flaw type towards the residual strength capability of a laminate turn out to be substantial as the notch size gets larger than one inch. Test results showed that a narrow slit or saw cut damage is far more critical than a circular hole cut-out. The notch sensitivity order of a saw cut flaw is also roughly three times more than that of a circular hole. Analytical studies were also performed to evaluate several finite element method variable effects on residual strength prediction and to discover the best practice in stress analyses of notched composite laminates. Point Stress failure criterion was used in the analyses and predicted failure loads were compared to the experimental data. Good agreements and correlations were found between the analytical predictions and the experimental data. It can be concluded that the residual strength of a notched laminated composite can be reasonably predicted from finite element analyses.Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Aerospace Engineering
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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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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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LOPES, BRUNO JORDAO. "DEVELOPMENT AND CHARACTERIZATION OF CARBON FIBER REINFORCED THERMOPLASTIC COMPOSITES." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2018. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=34967@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
O objetivo deste trabalho foi produzir, caracterizar e avaliar o comportamento mecânico de um compósito de matriz termoplástica (ABS) reforçado por fibras de carbono para uso futuro em manufatura aditiva. Misturas foram produzidas contendo diferentes quantidades (0 por cento, 5 por cento e 16,7 por cento) e comprimentos (3 mm e 6 mm) de fibras. Cada mistura foi processada através de uma extrusora dupla rosca para a produção de pellets. Os pellets de cada mistura (incluindo pellets de ABS puro) foram analisados para a caracterização do material processado. Posteriormente, corpos de prova foram extrusados para a determinação das propriedades mecânicas e análise da superfície de fratura. As técnicas utilizadas para a caracterização do material foram: espectroscopia no infravermelho (FTIR), análise termogravimétrica (TGA), reometria capilar e microscopia eletrônica de varredura (MEV). Para a avaliação do comportamento mecânico, os corpos de prova extrusados foram ensaiados para a determinação da resistência à tração, módulo de elasticidade e ductilidade. Em seguida, as superfícies de fratura dos corpos de prova foram analisadas no MEV. Foi verificada a possibilidade de degradação da matriz polimérica e formação de vazios durante o processamento inicial do material, que foram eliminados após a segunda extrusão. As fibras de carbono causaram aumento no módulo de elasticidade e diminuição da ductilidade do compósito, apesar de pouco influenciarem as propriedades reológicas. Além disto, pequenas variações na estabilidade térmica foram observadas. Ao final, em anexo, foi elaborado um panorama sobre a Manufatura Aditiva (MA) e a oportunidade de utilização de compósitos em técnicas de impressão 3D.
The goal of this work was to produce, characterize and analyze the mechanical behavior of a carbon fiber reinforced thermoplastic composite with future applications in additive manufacturing. Mixtures were produced with varying carbon fiber content (0 per cent, 5 per cent, and 16,7 per cent) and initial length (3 mm and 6 mm). Each mixture was processed via a twin-screw extruder to produce pellets. Pellets from each mixture (including pure ABS) were analyzed to investigate the processed material properties. Afterwards, test specimens were extruded from each mixture s pellets for mechanical testing and fracture surface analysis. The following techniques were used for material characterization: Fourrier-Transform Infrared Spectroscopy (FTIR), Thermogravimetric Analysis (TGA), capillary rheology and Scanning Electron Microscopy (SEM). For the evaluation of mechanical properties, the extruded test specimens yield strength, Young s modulus and ductility were determined. Also, the fracture surfaces were observed using SEM. The effects of processing parameters and of the introduction of carbon fibers in the ABS polymer were determined. Results pointed out the possibility of degradation during initial processing and the formation of voids in the pellets structure, which were eliminated during the second extrusion. Results also showed an increase in modulus and a decrease in ductility of the composite, whereas rheological properties seemed largely unaffected. Additionally, small variations in thermal stability were observed with varying carbon fiber content and length. Finally, as an annex, a brief overview of Additive Manufacturing and the opportunities for using carbon fiber reinforced thermoplastics in 3D printing techniques is presented.
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Rice, Kolten Dewayne. "Bending Behavior of Concrete Beams with Fiber/Epoxy Composite Rebar." BYU ScholarsArchive, 2019. https://scholarsarchive.byu.edu/etd/9062.
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This research explores the use of carbon/epoxy and fiberglass/epoxy fiber-reinforced polymer (FRP) composite rebar manufactured on a three-dimensional braiding machine for use as reinforcement in concrete beams under four-point bending loads. Multiple tows of prepreg composite fibers were pulled to form a unidirectional core. The core was consolidated with spirally wound Kevlar fibers which were designed to also act as ribs to increase pullout strength. The rebar was cured at 121â—¦C (250â—¦F) in an inline oven while keeping tension on the fibers. Five configurations of reinforcing bars were used in this study as reinforcement in concrete beam specimens: carbon/epoxy rebar and fiberglass/epoxy rebar were manufactured on the three-dimensional braiding machine and cured in an inline oven while still under tension immediately after production; carbon/epoxy rebar was manufactured by IsoTruss industries on the three-dimensional braiding machine and was rolled and stored before curing; fiberglass/epoxy rebar was purchased from American Fiberglass; conventional No. 4 steel rebar was also purchased. All bars were embedded in 152 cm (60 in) long, 11 cm (4.5 in) wide, and 15 cm (6.0 in) tall concrete beams. Beams were tested under four-point bending loads after which three 30 cm (12 in) specimens were taken from the ends of each configuration to be tested under axial compression loads in order to investigate the effects of the concrete voids on the concrete strength. Concrete beams reinforced with BYU glass/epoxy rebar manufactured on the three-dimensional braiding machine exhibited 5% greater compression bending stress and 11% greater tension bending stress than concrete beams reinforced with industry manufactured glass/epoxy rebar. Concrete beams reinforced with BYU carbon/epoxy rebar manufactured on the three-dimensional braiding machine exhibited 18% lower compression bending stress and 64% lower tension bending stress than concrete beams reinforced with industry manufactured carbon/epoxy rebar. BYU glass/epoxy rebar has a 3% greater stiffness and 1% greater displacement than industry manufactured glass/epoxy rebar and BYU carbon/epoxy rebar has a 40% greater bending stiffness and 19% lower displacement than industry carbon/epoxy rebar. BYU carbon/epoxy rebar has 49% lower compression bending stress, 1% lower tension bending stress, 28% lower displacement, and a 68% greater bending stiffness than BYU glass/epoxy rebar. BYU glass/epoxy rebar has 38% greater compression bending stress, 30% lower tension bending stress, 26% greater center displacement, and a 105% lower bending stiffness than conventional steel. BYU carbon/epoxy rebar has 8% lower compression bending stress, 31% lower tension bending stress, and 22% lower bending stiffness than steel. The deflections of steel reinforced concrete and BYU carbon/epoxy reinforced concrete are comparable with steel rebar displaying a 1% greater center displacement than BYU carbon/epoxy rebar.
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Yoo, Jong Hyun. "Tribological behavior of unfilled and carbon fiber reinforced polyether ether ketone/polyether imide composites." Thesis, This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-12302008-063612/.
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Vijayakumar, Dineshwaran. "Manufacturing Carbon Nanotube Yarn Reinforced Composite Parts by 3D Printing." University of Cincinnati / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1481031494735314.
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Richard, Brandon Demar. "Thermal Infrared Reflective Metal Oxide Sol-Gel Coatings for Carbon Fiber Reinforced Composite Structures." Scholar Commons, 2013. http://scholarcommons.usf.edu/etd/4569.
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Recent trends in composite research include the development of structural materials with multiple functionalities. In new studies, novel materials are being designed, developed, modified, and implemented into composite designs. Typically, an increase in functionality requires additional material phases within one system. The presence of excessive phases can result in deterioration of individual or overall properties. True multi-functional materials must maintain all properties at or above the minimum operating limit. In this project, samples of antimony and cobalt-doped tin oxide (ATO(Co2O3)) sol-gel solutions are used to coat carbon fibers and are heat treated at a temperature range of 200 - 500 °C. Results from this research are used to model the implementation of sol-gel coatings into carbon fiber reinforced multifunctional composite systems. This research presents a novel thermo-responsive sol-gel/ (dopant) combination and evaluation of the actuating responses (reflectivity and surface heat dissipation) due to various heat treatment temperatures. While ATO is a well-known transparent conductive material, the implementation of ATO on carbon fibers for infrared thermal reflectivity has not been examined. These coatings serve as actuators capable of reflecting thermal infrared radiation in the near infrared wavelengths of 0.7-1.2 μm. By altering the level of Co2O3 and heat treatment temperatures, optimal optical properties are obtained. While scanning electron microscopy (SEM) is used for imaging, electron diffraction
spectroscopy (EDS) is used to verify the compounds present in the coatings. Fourier transform infrared (FT-IR) spectroscopy was performed to analyze the chemical bonds and reflectivity in the infrared spectra after the heat treatments. Total reflection and angle-dependent reflectivity measurements were performed on the coatings in the wavelengths of 0.7-2 μm. Laser induced damage threshold testing was done to investigate the dielectric breakdown and used to calculate surface temperatures.
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Labronici, Marcos. "Effect of silicone interlayer on carbon fiber reinforced PMR-15 composite: Processing and characterization." Case Western Reserve University School of Graduate Studies / OhioLINK, 1994. http://rave.ohiolink.edu/etdc/view?acc_num=case1061308467.
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Rubin, Ariel. "Strenghtening of reinforced concrete bridge decks with carbon fiber composites." Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/19320.
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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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Chin, Joannie W. "Surface characterization and adhesive bonding of carbon fiber-reinforced composites." Diss., This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-10032007-171739/.
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Lee, James Khian-Heng. "Alternative Carbon Fiber Reinforced Polymer (CFRP) Composites for Cryogenic Applications." MSSTATE, 2004. http://sun.library.msstate.edu/ETD-db/theses/available/etd-04082004-154654/.
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A cheaper access to space is needed in current times and new technologies need to be developed to reduce the cost of space access to increase productivity. This thesis presents a study on carbon fiber reinforced polymer (CFRP) composites which is an enabling technology for cost reduction in space vehicles. A literature review of the behavior of CFRP composite has been conducted and it was found that the currently used IM7/977 carbon fiber reinforced epoxy composites do not microcrack at a lower number of thermal cycles. Nano-composites and Thermoplastic matrix composites have been found as two promising alternatives for cryogenic applications. With the use of nano sized inclusions in currently used epoxy resins, coefficient of thermal expansion can be reduced while increase in strength and fracture toughness can be achieved. Some thermoplastics were found to have non-linear stress-strain relationships with signs of ductility even at 4.2K. Both of these resin systems show promise in reducing microcracking at cryogenic temperatures.
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Chennakesavelu, Ganesh. "Orthogonal machining of uni-directional carbon fiber reinforced polymer composites." Thesis, Wichita State University, 2010. http://hdl.handle.net/10057/3473.
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This research basically deals with Orthogonal Machining of Unidirectional Carbon Fiber
Reinforced Polymer (FRP) Composites as secondary operations like machining is a very
important process in composites manufacturing. Even though composites are manufactured to
near net shape, machining operations becomes obvious to attain dimensional accuracy and
surface finish for further assembly operations. The machining of FRP’s is different and more
complicated to that of metals because of their anisotropic and inhomogeneous nature, along with
the chip formation mode for its brittle behavior. Fibers are very abrasive in nature and cause
extreme tool wear making it difficult for cutting and when combined with matrix which is
comparatively weak produce fluctuating force on the tool to augment for the tool wear. It will be
very helpful to study their behavior for optimizing the machining condition and to minimize the
above mentioned drawbacks.
This work will be basically dealing on the experimental study and numerical prediction
of machining quality during orthogonal machining on various fiber orientation and cutting
conditions. Orthogonal machining was performed using 3-axis miniMILL for experimental work
and commercially available simulation software ABAQUS 6.9-2 for numerical study. The
numerical findings are presented to supplement experimental work for predicting delamination
which is very important for its service life along with some interesting observation which is
discussed in this report.Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering.
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Gudimani, Gurusiddeshwar. "Oblique machining of uni directional carbon fiber reinforced polymer composites." Thesis, Wichita State University, 2011. http://hdl.handle.net/10057/3956.
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Composite materials have a wide range of applications in aerospace and automotive industries due to the advantage of their tailorability when manufacturing. These materials are manufactured near net shape but post-production machining is required where it cannot be avoided like holes, cutouts and doors to achieve dimensional accuracies and for further assemblies. Oblique machining is one of the important processes as to achieve the above. The machining of composites is different from that of metals due to the anisotropic and inhomogeneity of the material. Because of this nature the machining process becomes complicated. The fiber being abrasive in nature and matrix being soft and weak produce fluctuating forces and make difficult for the cutting process causing tool wear. This research hence concentrates on the oblique machining of Uni-directional carbon fiber reinforced polymer composites (UD-CFRP). The oblique cutting of these UD-CFRP‟s are carried out at different rake angles and at different fiber orientations i.e. from 0 to 180 to predict the different forces. These results are compared with the numerical results where a finite element model is modeled for these different conditions and are compared with the experimental results. The oblique machining is a 3-dimensional process unlike the orthogonal machining which is a 2-dimensional process. The finite element model is modeled as a single-phase system by considering the material to be equivalent homogeneous material for analysis purpose, which simplifies for force prediction. The results from the experiments and the finite element analysis can be used for further analysis where multiple layers of composite laminates are used with different fiber orientations. The results can also be used to predict the forces for drilling process by considering the drilling process to be combination of the oblique cutting at each point.Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering.
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Rodriguez, Alejandro Jose. "Processing and characterization of carbon nanoparticle/fiber-reinforced polymer composites." Diss., Wichita State University, 2010. http://hdl.handle.net/10057/3467.
Full textAbstract:
Carbon nanotubes (CNTs) and carbon nanofibers (CNFs) have an exceptional combination of
properties that make them ideal materials for use as reinforcing particles in advanced composites.
This investigation was aimed at obtaining fundamental understanding of the processing and
properties of carbon nanoparticle/fiber-reinforced polymer composites ―defined as multiscalereinforced
polymer composites (MRPCs)― manufactured through a practical and scalable
process. Such process consists of two stages. The first stage involves the synthesis of multiscalereinforcement
fabrics (MRFs) by electrophoretic deposition of carboxylic acid- or aminefunctionalized
CNTs and CNFs onto the surface of carbon fiber layers in aqueous medium; while
the second stage proceeds with the stacking of the MRFs and infusion of the resulting preforms
with an epoxy-amine resin system to obtain the MRPC.
MRPCs manufactured following the described approach were tested for
mechanical and electrical properties. Mechanical test results showed an increase in interlaminar
shear strength (ILSS), shear stiffness, and compressive strength of all panels manufactured.
Panels containing amine-functionalized carbon nanoparticles had the highest increase in
properties: 13% in ILSS, 2.5-4 fold in shear stiffness, and up to 15% in compressive strength. On
the other hand, it was found that through-plane electrical conductivity of MRPCs increased by
100% when using unsized MRFs. Investigation into the enhancement mechanism of mechanical
and electrical properties was also performed. Discussion of these mechanisms are presented with
emphasis placed on the fiber/matrix interface and the load transfer mechanisms between matrix,
carbon nanoparticles, and carbon fiber.Thesis (Ph.D.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering
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DeValve, Caleb Joshua. "Investigations on Void Formation in Composite Molding Processes and Structural Damping in Fiber-Reinforced Composites with Nanoscale Reinforcements." Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/19290.
Full textAbstract:
Fiber-reinforced composites (FRCs) offer a stronger and lighter weight alternative to traditional materials used in engineering components such as wind turbine blades and rotorcraft structures. Composites for these applications are often fabricated using liquid molding techniques, such as injection molding or resin transfer molding. One significant issue during these processing methods is void formation due to incomplete wet-out of the resin within the fiber preform, resulting in discontinuous material properties and localized failure zones in the material. A fundamental understanding of the resin evolution during processing is essential to designing processing conditions for void-free filling, which is the first objective of the dissertation. Secondly, FRCs used in rotorcraft experience severe vibrational loads during service, and improved damping characteristics of the composite structure are desirable. To this end, a second goal is to explore the use of matrix-embedded nanoscale reinforcements to augment the inherent damping capabilities in FRCs.The first objective is addressed through a computational modeling and simulation of the infiltrating dual-scale resin flow through the micro-architectures of woven fibrous preforms, accounting for the capillary effects within the fiber bundles. An analytical model is developed for the longitudinal permeability of flow through fibrous bundles and applied to simulations which provide detailed predictions of local air entrapment locations as the resin permeates the preform. Generalized design plots are presented for predicting the void content and processing time in terms of the Capillary and Reynolds Numbers governing the molding process.
The second portion of the research investigates the damping enhancement provided to FRC\'s in static and rotational configurations by different types and weight fractions of matrix-embedded carbon nanotubes (CNTs) in high fiber volume fraction composites. The damping is measured using dynamic mechanical analysis (DMA) and modal analysis techniques, and the results show that the addition of CNTs can increase the material damping by up to 130%. Numerical simulations are conducted to explore the CNT vibration damping effects in rotating composite structures, and demonstrate that the vibration settling times and the maximum displacement amplitudes of the different structures may be reduced by up to 72% and 50%, respectively, with the addition of CNTs.
Ph. D.
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Lee, Stephen Kim Lon. "Flexural strength of reinforced concrete beams strengthened using carbon fibre reinforced composite sheets." Thesis, University of Southampton, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.420192.
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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.
Full textAbstract:
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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Esposito, Alessandro. "Creep deflection of low-strength reinforced concrete flexural members strengthened with carbon fiber composite sheets." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/10340/.
Full textAbstract:
The low-strength concrete is defined as a concrete where the compressive cubic strength is less than 15 MPa. Since the beginning of the last century, many low-strength concrete buildings and bridges have been built all over the world. Being short of deeper study, composite sheets are prohibited in strengthening of low-strength reinforced concrete members (CECS 146; ACI 440). Moreover, there are few relevant information about the long-term behavior and durability of strengthened RC members.
This fact undoubtedly limits the use of the composite materials in the strengthening applications, therefore, it is necessary to study the behaviours of low-strength concrete elements strengthened with composite materials (FRP) for the preservation of historic constructions and innovation in the strengthening technology.
Deformability is one of criteria in the design of concrete structures, and this for functionality, durability and aesthetics reasons. Civil engineer possibly encounters more deflection problems in the structural design than any other type of problem. Many materials common in structural engineering such as wood, concrete and composite materials, suffer creep; if the creep phenomenon is taken into account, checks for serviceability limit state criteria can become onerous, because the creep deformation in these materials is in the same order of magnitude as the elastic deformation.
The thesis presents the results of an experimental study on the long-term behavior of low-strength reinforced concrete beams strengthened with carbon fiber composite sheets (CFRP). The work has investigated the accuracy of the long-term deflection predictions made by some analytical procedures existing in literature, as well as by the most widely used design codes (Eurocode 2, ACI-318, ACI-435).
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Khasawneh, Firas Abdallah. "Characterization of drillability of sandwich structure of carbon fiber reinforced epoxy composite over titanium alloy." Diss., Columbia, Mo. : University of Missouri-Columbia, 2006. http://hdl.handle.net/10355/5871.
Full textAbstract:
Thesis (M.S.)--University of Missouri-Columbia, 2006.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on September 13, 2007). Vita. Includes bibliographical references.
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Ashok, Kumar Sachin Sharma. "Incorporation of graphene thin films into the carbon fiber reinforced composite via 3d composite concept against the lightning strikes on composite aircraft." Thesis, Wichita State University, 2012. http://hdl.handle.net/10057/5592.
Full textAbstract:
Research and development of graphene and graphene based materials have been increasing significantly since they were invented. This report presents the development of a highly conductive graphene thin film (GTF) to reduce the damage of lightning effects on composite aircrafts. Furthermore, there are three new developments that are presented in this research: (a) the development of a highly conductive functionalized nanosize GTF, (b) a new approach of incorporating the GTF into the carbon fiber reinforced composite panel, and (c) a new development of 3D stitching concept were introduced specifically using polyester threads instead of fiber yarns that can be useful for the applications of aircraft protections against the effects of lightning strike. In addition, graphene was chemically functionalized and oxidized to form GTF. The highest electrical conductivity measured on the GTF was approximately 1800 S/cm. Furthermore, the GTF was then incorporated into the carbon fiber reinforced composite. Delamination was observed between the GTF and the composite. To investigate this issue, the composite was mechanically tested and there was a 40% decrease in tensile strength compared to the baseline. Therefore, 3D stitching concept was then introduced to reduce the delamination. Four stitch configurations having different stitch length, thread to thread thickness, thread tension, and thread thickness respectively were used in this study. 3D stitching was initially done on six sheets of unidirectional prepreg, MTM45-1 without the incorporation of GTF. Furthermore, mechanical testing was carried out and the stitch configuration that delivered the most appropriate result was then further used on twelve sheets of unidirectional prepreg, 5320. Here, three samples which was the baseline, 5320 with and without the incorporation of GTF respectively were prepared and mechanically tested, and the strength values were observed.Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering
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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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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.
Full textAbstract:
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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Yari, Boroujeni Ayoub. "Fatigue, Fracture and Impact of Hybrid Carbon Fiber Reinforced Polymer Composites." Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/84223.
Full textAbstract:
The excellent in-plane strength and stiffness to-weight ratios, as well as the ease of manufacturing have made the carbon fiber reinforced polymer composites (CFRPs) suitable structural materials for variety of applications such as aerospace, automotive, civil, sporting goods, etc. Despite the outstanding performance of the CFRPs along their fibers direction (on-axis), they lack sufficient strength and performance in the out-of-plane and off-axis directions. Various chemical and mechanical methods were reported to enhance the CFRPs' out-of-plane performance. However, there are two major drawbacks for utilizing these approaches: first, most of these methods induce damage to the carbon fibers and, therefore, deteriorate the in-plane mechanical properties of the entire CFRP, and second, the methods with minimal deteriorating effects on the in-plane mechanical performance have their own limitations resulting in very confined mechanical performance improvements. These methods include integrating nano-sized reinforcements into the CFRPs' structure to form a hybrid or hierarchical CFRPs.
In lieu to all the aforementioned approaches, a relatively novel method, referred to as graphitic structures by design (GSD), has been proposed. The GSD is capable of grafting carbon nanotubes (CNTs) onto the carbon fibers surfaces, providing high concentration of CNTs where they are most needed, i.e. the immediate fiber/matrix interface, and in-between the different laminae of a CFRP. This method shows promising improvements in the in-plane and out-of-plane performance of CFRPs. Zinc oxide (ZnO) nanorods are other nano-sized reinforcing structures which can hybridize the CFRPs via their radially growth on the surface of carbon fibers. Among all the reported methods for synthesizing ZnO nanorods, hydrothermal technique is the most straightforward and least destructive route to grow ZnO nanorods over carbon fibers.
In this dissertation, the GSD-CNTs growth method and the hydrothermal growth of ZnO nanorods have been utilized to fabricate hybrid CFRPs. The effect of different ZnO nanorods growth morphologies, e.g. size distribution and alignment, on the in-plane tensile performance and vibration attenuation capabilities of the hybrid CFRPs are investigated via quasi-static tension and dynamical mechanical analysis (DMA) tests, respectively. As a result, the in-plane tensile strength of the hybrid CFRPs were improved by 18% for the composite based on randomly oriented ZnO nanorods over the carbon fibers. The loss tangent of the CFRPs, which indicates the damping capability, increased by 28% and 19% via radially and randomly grown ZnO nanorods, respectively.
While there are several studies detailing the effects of dispersed nanofillers on the fracture toughness of FRPs, currently, there are no literature detailing the effect of surface GSD grown CNTs and ZnO nanowire -on carbon fiber- on the fracture toughness of these hybrid composites. This dissertation probes the effects of surface grown nano-sized reinforcements on the fracture toughness via double cantilever beam (DCB) tests on hybrid ZnO nanorod or CNT grafted CFRPs. Results show that the surface grown CNTs enhanced the Mode I interlaminar fracture toughness (GIc) of the CFRPs by 22% and 32%, via uniform and patterned growth morphologies, respectively, over the reference composite based on untreated carbon fiber fabrics.
The dissertation also explains the basis of the improvements of the fracture toughness via finite element method (FEM). In particular, FEM was employed to simulate the interlaminar crack growth behavior of the hybrid CFRPs under Mode I crack opening loading conditions embodied by the DCB tests. These simulations revealed that the hybrid CFRP based on fibers with uniform surface grown MWCNTs exhibited 55% higher interlaminar strength compared to the reference CFRPs. Moreover, via patterned growth of MWCNTs, the ultimate crack opening resistance of the CFRPs improved by 20%. To mimic the experimental behavior of the various CFRPs, a new methodology has been utilized to accurately simulate the unstable crack growth nature of CFRPs.
Several investigations reported the effects of adding nanomaterials-including CNTs- as a filler phase inside the matrix material, on the impact energy absorption of the hybrid FRPs. However, the impact mitigation performance of CFRPs based on ZnO nanorod grafted carbon fibers has not been reported. The dynamic out-of-plane energy dissipation capabilities of different hybrid composites were investigated utilizing high velocity (~90 m/s) impact tests. Comparing the results of the hybrid MWCNT/ZnO nanorod/CFRP with those of reference CFRP, 21% and 4% improvements were observed in impact energy absorption and tensile strain to failure of the CFRPs, respectively.
In addition to elevated stiffness and strength, CFRPs should possess enough tolerance not only to monotonic loadings, but also to cyclic loadings to be qualified as alternatives to traditional structural metal alloys. Therefore, the fatigue life of CFRPs is of much interest. Despite the promising potential of incorporating nano-sized reinforcements into the CFRPs structure, not many studies reported on the fatigue behavior of hybrid CFRPs so far. In particular, there are no reported investigations to the effect of surface grown CNTs on the fatigue behavior of the hybrid CFRPs, due to fact that almost all the CNT growth techniques (except for the GSD method) deteriorated the in-plane performance of the hybrid CFRPs. The hybrid ZnO nanorod grafted CFRPs have not been investigated under fatigue loading as well. In this dissertation, different hybrid CFRPs were tested under tension-tension fatigue to reveal the effects of the different nano-reinforcements growth on the fatigue behavior of the CFRPs. A remarkable fatigue damage tolerance was observed for the CFRPs based on uniform and patterned grown CNT fibers. Almost two decades of fatigue life extension was achieved for CFRPs based on surface grown MWCNTs.Ph. D.
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CURTY, LARISSA AZEVEDO. "EXPERIMENTAL STUDY OF REINFORCED CONCRETE SHORT CORBELS WITH CARBON FIBER COMPOSITES." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2009. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=32821@1.
Full textAbstract:
PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
PROGRAMA DE SUPORTE À PÓS-GRADUAÇÃO DE INSTS. DE ENSINO
Este trabalho é uma pesquisa experimental realizada no Laboratório de Estruturas e Materiais da PUC–Rio, utilizando–se a técnica de aplicação do compósito de fibras de carbono (CFC) colados externamente em consoles curtos de concreto armado. Foram ensaiados seis consoles curtos, sendo: um de referência, três com reforço de CFC na horizontal e dois com reforço de CFC na diagonal. A resistência média do concreto aos 28 dias foi de 30 MPa. A seção transversal do pilar foi de 25 cm × 50 cm e a seção do transversal console foi de 25 cm × 37,5 cm. O diâmetro da armadura tracionada em laço era de 10 mm e o diâmetro da armadura de costura era de 6,3 mm. Os consoles foram instrumentados com extensômetros elétricos de resistência na armadura tracionada, no estribo, no concreto e no CFC. Os ensaios comprovaram um razoável desempenho dessa técnica de reforço. Os resultados experimentais foram comparados com os resultados obtidos no modelo de Bielas e Tirantes e no modelo cinemático da Teoria da Plasticidade, visando a comparação das forças verticais últimas teóricas e experimentais. Foi avaliado o ângulo de inclinação das bielas e o fator de efetividade da deformação específica no reforço de CFC.
This work is an experimental research of concrete short corbels wrapped with Carbon Fiber Reinforced Polymer (CFRP) strips. Different strengthening configurations were used. Was carried out on six corbels strengthened by CFRP. One control specimen without CFRP, three corbels with horizontal CFRP strips and two corbels with diagonal CFRP strips. The concrete had a 28 day compressive strength of 30 MPa. The column cross-section dimensions were 25 cm x 50 cm and the corbel cross-section dimensions were 25 cm x 37,5 cm. The flexural reinforcement consisted of four deformed bars each of diameter 10 mm with four transverse bars of diameter 6,3 mm. The corbels were instrumented with strain gages in flexural reinforcement, stirrup, concrete surface and CFRP strips. The analytical models based on Strut-and-Tie model and in the kinematic model of the Theory of Plasticity, allows one to determine the bearing capacity of corbels. The experimental values are then compared with the analytical results, showing good agreement. The strut angle and the strengthening effectiveness were evaluated.
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Sarles, Stephen Andrew. "Active Rigidization of Carbon Fiber Reinforced Composites via Internal Resistive Heating." Thesis, Virginia Tech, 2006. http://hdl.handle.net/10919/31570.
Full textAbstract:
The use of inflatable, rigidizable structures in solar arrays and other space structures has the potential to drastically reduce the weight, volume, and cost of placing payloads into orbit. Inflatable components consist of ultra-lightweight, flexible materials that enable compact packaging prior to launch. These structures are then transformed from their initially flexible state to one that offers permanent shape-holding and structural integrity through a tailored rigidization process. Inflatable spacecraft must be impervious to the environmental conditions in space--such as ionizing radiation, UV and particle radiation, atomic oxygen, and impacts from space debris and meteoroids. They must also exhibit stable operation over a useful storage and mission life. Methods for causing rigidization in inflatable spacecraft include both passive and active techniques. Passive techniques rely on an uncontrolled, unprovoked reaction between the rigidizable materials in the structure and the surrounding space environment. The benefits of a passive system are offset by their inherent lack of control, which can lead to long curing times and weak spots due to uneven curing.
This work presents internal resistive heating as an alternative approach for inducing matrix consolidation and curing of thermoset-coated carbon fiber tows. The ability to dictate this physical transformation through temperature-controlled resistive heating highlights the responsive nature of thermoset polymer composites and demonstrates the advantages of active rigidization. Feedback temperature control is implemented so as to provide a reliable, robust heating method for prescribing material-specific curing profiles. Resistive heating curing schedules developed from previous thermal analysis on two resins, U-Nyte Set 201A and 201B, are prescribed for samples of carbon fiber tow coated with each resin. The rigidization success of each curing profile is then evaluated with respect to both the increase in mechanical stiffness and the cure completion. These experiments indicate that rigidizing the coated fiber tow results in a composite material that is 20 times stronger in bending than prior to curing. The stiffening process requires roughly 1W-hr of energy with 5W peak power over the course of a 24-minute curing schedule. Curing temperature, curing time, and heating rate are also individually varied to determine their effect on rigidization as well as develop methods for reducing curing time and energy. The rigidization of an inflatable structure culminates this work and demonstrates the ability to achieve real strengthening through temperature-controlled internal resistive heating.Master of Science
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Bullions, Todd Aaron. "Manufacture of and Environmental Effects on Carbon Fiber-Reinforced PhenylEthynyl-Terminated Poly(EtherImide)." Diss., Virginia Tech, 2000. http://hdl.handle.net/10919/28962.
Full textAbstract:
The initial objective of this research project was to determine the feasibility of manufacturing carbon fiber-reinforced (CFR) composites with a matrix consisting of a phenylethynyl-terminated version of a thermoplastic poly(etherimide) termed PETU. Successful composite manufacture with 3,000 g/mol (3k) PETU led to a survey of CFR 3kPETU mechanical properties for comparison with other high-performance composites. Encouraging results led to a study of moisture sorption effects on CFR 3kPETU properties. The success of these initial studies spawned the large scale production of 2,500 g/mol (2.5k) PETU.
Thermal characterization of neat and CFR 2.5kPETU via differential scanning calorimetry, dynamic mechanical thermal analysis, and parallel plate rheometry resulted in an understanding of the influence of cure time and temperature on reaction progress via both reaction kinetics and monitoring of the glass transition temperature. From the rheological characterization, a two-stage, dual-Arrhenius model was developed to successfully model isothermal complex viscosity over the range of processing temperatures.
Neat 2.5kPETU and CFR 2.5kPETU specimens were exposed separately to elevated temperature environments of different moisture and different oxygen concentrations to evaluate the effects of moisture absorption, moisture desorption, and thermal oxidation on material properties. Moisture absorption took place in a 90 °C / 85% relative humidity environment followed by moisture desorption in a 90 °C / 10% relative humidity environment. Thermal-oxidative aging for up to 5000 hours took place at 204 204 °C in environments of four different oxygen partial pressures: 0.0 kPa, 2.84 kPa, 20.2 kPa, and 40.4 kPa. Following exposure to the different aging environments, the specimens were tested for retention of mechanical properties. In addition, moisture sorption properties were measured.
Results from the moisture sorption studies on CFR 3kPETU and CFR 2.5kPETU suggest that fully cured composites will withstand moisture absorption and desorption with negligible effects on mechanical properties, whereas, lack of full cure allows moisture sorption to permanently damage the composites. Despite a lack of mass loss or visual evidence of degradation following thermal-oxidative aging, a decline in mechanical properties was observed with the reduction becoming greater with longer aging times and higher oxygen partial pressures.Ph. D.
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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.
Full textAbstract:
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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Matemilola, Saka Adelola. "Impact damage to composite materials." Thesis, University of Cambridge, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319939.
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Zulu, Andrew Wisdom. "Thick Composite Properties and Testing Methods." Thesis, KTH, Lättkonstruktioner, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-243885.
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In most application to date reinforced carbon fiber composites have been used in relatively smaller thickness, less than 10mm thick and essentially for carrying in-plane loads. As a result, design and testing procedures were developed which reflected the need to understand the in-plane response of the material. recently, engineers and designers have begun to use reinforced carbon fiber composites in thicker sections, where an understanding of the through-thickness response is of para-mount importance in designing reliable structures, particularly where the through-thickness strength has a controlling influence on the overall structural strength of the component. In this thesis tests will be done on carbon fiber non-crimp fabric (NCF) which will be loaded in compression and shear and elastic moduli and strength will be evaluated. In characterizing the through-thickness mechanical properties of a composite, the objective is to produce a state of stress in the test specimen which is uniform and will repeatedly measure the true properties with accuracy. In this study, specimens were machined from two blocks of thick (~20 mm) laminates of glass/epoxy and NCF carbon fiber infused with vinylester and tested in compression, and shear.
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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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Kulkarni, Mandar Madhukar. "Prediction of Elastic Properties of a Carbon Nanotube Reinforced Fiber Polymeric Composite Material Using Cohesive Zone Modeling." University of Cincinnati / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1235433423.
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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.
Full textAbstract:
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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Bruhschwein, Taylor John. "Identification of Delamination Defects in CFRP Materials through Lamb Wave Responses." Thesis, North Dakota State University, 2014. https://hdl.handle.net/10365/27328.
Full textAbstract:
Delamination is currently a largely undetectable form of damage in composite laminate materials. This thesis will develop a method to more easily detect delamination damage within composite materials. Using finite element analysis modeling and lab testing, a new method from interpreting the results obtained from existing structural health monitoring techniques is developed. Lamb waves were introduced and recorded through an actuator and sensors made of piezoelectric material. The data was then analyzed through a novel data reduction method using the Fast Fourier Transform (FFT). Using the data from FFT, the idea of covariance of energy change was developed. By comparing the covariance of energy change in beams with differing delamination size, thickness and depth, correlations were able to be developed. With these correlations, the severity and of damage was able to be detected.
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Wilkinson, Steven P. "Toughened bismaleimides, their carbon fiber composites and interphase evaluation studies." Diss., Virginia Tech, 1991. http://hdl.handle.net/10919/38782.
Full textAbstract:
The concept of employing engineering thermoplastics as toughness modifiers for Bismaleimide resins was utilized to improve the fracture toughness properties of these important materials, which have applications as matrix resins for high performance composites. Modifier molecular weight, end group functionality, backbone structure and weight percent incorporation were all studied with respect to their influence on Kj, fracture toughness properties. Increases in fracture toughness were created with thermoplastic oligomers without sacrificing high temperature properties and desirable hot-melt processing conditions. Investigations were also made to study the morphological features that develop within these modified thermosets and their resistance to specific environments. In addition, unidirectional carbon fiber composites were prepared and their mode | and II strain energy release rates measured. Respectable increases in the interlaminar fracture toughness were obtained, 15 and 20 percent by weight loadings of maleimide terminated polysulfone modifiers yielded Gj, values of 489425 and 734+10 Jim2 respectively, a substantial improvement over the control value of 359+17 J/im2.
Laminates were prepared using carbon fibers that had been investigated in terms of their surface energies using Inverse Gas Chromatography. It was illustrated how this technique could distinguish between the acid-base properties of fibers possessing different degrees of proprietary surface treatments. Fiber composites containing both contrasting and subtle changes at the fiber-matrix interphase were prepared and their mechanical properties evaluated using a variety of test methods. Dramatic increases in laminate properties were measured for composites possessing contrasting interphases. Furthermore, the mode II fracture toughness test was sensitive to interphase differences; however, the mode | fracture toughness test was not.
Specimens subjected to the new Continuous Ball Indentation test method (mesoindentation) were compared with single fiber micro-indentation test results. Differences were detected in composites prepared using untreated and surface treated fibers. The new method was also sensitive to changes in matrix ductility. Certain anomalies that were noted to be surprising from micro-indentation measurements were not present in the meso-indentation test results. These observations brought to light certain limitations found within the micro-indentation test, but further supported the new test method as a potential technique for fiber-matrix interphase evaluation.Ph. D.
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Tam, Yee Kam. "Mechanism study of carbon nanotube reinforced ultra-high molecular weight polyethylene fibers /." View abstract or full-text, 2008. http://library.ust.hk/cgi/db/thesis.pl?CBME%202008%20TAM.
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