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1
Farrow, G. J. "Acoustic emission in carbon fibres and carbon fibre reinforced plastics." Thesis, University of Salford, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334022.
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Wong, Doris Wai-Yin. "Toughening of epoxy carbon fibre composites using dissolvable phenoxy fibres." Thesis, Queen Mary, University of London, 2013. http://qmro.qmul.ac.uk/xmlui/handle/123456789/8710.
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The aim of this study is to investigate a novel toughening approach for liquid mouldable carbon fibre/epoxy composites. The toughening mechanism is based on the use of thermoplastics for the toughening of epoxy resins in which polymer blends are formed, leading to phase separated morphologies which allows for various toughening mechanisms to take place. Instead of standard melt or solution blending, the thermoplastic in this study is introduced as solid phenoxy fibres, which are combined with dry carbon fabric preforms. These phenoxy fibres remain solid during resin infusion and dissolve when the laminates are heated and phase separation takes place before curing completed. The main benefits of this approach are that the viscosity of matrix resin remains low, which makes liquid moulding of these laminates possible. Localised and selective toughening of particular regions within a structure can also be achieved. Process time and cost can also be reduced by eliminating the polymer blending process. It was found that modification with phenoxy improved composite Mode-I interlaminar toughness significantly, with an increase of up to 10-folds for bifunctional epoxy composite and 100% for tetrafunctional epoxy composite, while tensile properties were not adversely affected. It was found that it is possible to combine the dissolvable phenoxy fibres with an undissolved aramid interleaf to improve toughness and damage properties. However, the phenoxy-epoxy systems had lowered environmental stability and degraded after hot-wet and solvent conditioning.
3
Liu, Wenjiao. "Electromechanical response of carbon nanotube/carbon fibre epoxy composites." Thesis, McGill University, 2014. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=123267.
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Carbon fibre (CF) reinforced polymers have become the most widely used composites in theaerospace industry. However, ensuring the integrity of composite structures remains one of themain challenges. By measuring the change in electrical resistance of these materials, it is feasibleto monitor strains and damage initiation and accumulation in-situ and in real-time. The objectiveof this work is to investigate the potential of adding carbon nanotubes (CNTs) to existing CFpolymersto improve strain self-sensing. First, the DC and AC conductivities of epoxy containingdifferent CNT weight concentrations are measured in order to characterize the percolationthreshold. Second, the variation in electrical resistance as a function of electrode distance isinvestigated for CF-epoxy and CF-CNT-epoxy composites. The results show that the addition ofCNTs increases through-thickness conductivity by primarily reducing CF-CF contact resistancerather than increasing the number of CF-CF contacts. In addition, the presence of CNTsengenders a more homogeneous CF-CF contact resistance distribution. Third, theelectromechanical behaviours of CF-epoxy and CF-CNT-epoxy composites are compared viatension, compression, and flexure experiments while simultaneously monitoring electricresponses. The addition of CNTs results in: 1) improved sensitivity under compression due to thecreation of more CF-CF contacts; 2) better linearity under tension due to a more gradual changein CF-CF contact resistance; 3) better electric response reproducibility and repeatability due tomore homogeneous distribution of CF-CF contact resistance. Finally, an existing analyticalmodel is modified to estimate the change in surface resistance on both the tension andcompression sides of flexural specimens using the results of tension- and compression-only testsas inputs. The modelling data is then compared with the measured change in surface resistanceunder flexural load and shows good agreement. The model advances CF-CF contact as thedominating mechanism in the change of surface resistance under mechanical loading—especiallyin compression.Les polymères à fibre de carbone (FC) sont de nos jours les composites les plus largementutilisés dans le domaine aéronautique. Cependant, assurer l'intégrité de ces structures compositesreste l'un des principaux défis. En mesurant la variation de la résistance électrique descomposites polymère-FC, il est possible de surveiller les déformations et les dommages in-situen temps réel. L'objectif de ce travail est d'étudier l'influence de l'addition de nanotubes decarbone (NTCs) dans des polymère-FC sur la capacité d'auto-détection des déformations et desendommagements structurels. Premièrement, les conductivités continues et alternatives derésines époxy contenant différentes concentrations en poids de NTC sont mesurées afin decaractériser le seuil de percolation. Deuxièmement, la variation de la résistance électrique enfonction de la distance de l'électrode est étudiée pour les composites époxy-FC et époxy-CFNTC. Les résultats démontrent que l'ajout de NTC augmente la conductivité à travers l'épaisseur,en réduisant principalement la résistance de contact FC-FC plutôt que d'augmenter le nombre decontacts FC-FC. De plus, l'ajout de NTC permet une répartition plus homogène de la résistancedes contacts FC-FC. Troisièmement, les comportements électromécaniques peuvent êtrecomparés en mesurant les réponses électriques d'échantillons en temps réel soumis à des tests detraction, compression, et flexion. L'ajout de NTC conduit à: 1) une amélioration de la sensibilitésous contraintes de compression due à davantage de contacts FC-FC créés, 2) une meilleurelinéarité de la résistance électrique sous contraintes de traction due à un changement plusprogressif de la résistance de contact FC-FC, 3) une meilleure reproductibilité et répétabilité desréponses électriques grâce à une répartition plus homogène de la résistance de contact FC-FC.Enfin, un modèle analytique est modifié pour estimer la variation de la résistance de surface enflexion en utilisant les résultats des essais de traction et de compression comme donnéesd'entrée. Les données obtenues par le modèle sont ensuite comparées avec la variation de larésistance de surface mesurée lors des essais en flexion, et présentent une bonne corrélation. Cemodèle démontre en plus que la variation des contacts FC-FC domine la variation de résistancede surface sous chargement mécanique, en particulier la compression.
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Ibarra, Gonzalez Nagore. "Carbon nanotube staple yarn/carbon composites in fibre form." Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708995.
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Thornton, Matthew James. "Catalytic carbon deposition on 3-dimensional carbon fibre supports." Thesis, University of Nottingham, 2005. http://eprints.nottingham.ac.uk/10137/.
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Catalytic carbon deposition reactions, using methane, ethane or synthetic natural gas (1.8 vol. % propane, 6.7 vol. % ethane and balance methane) as the carbon-containing gas feedstock with or without the addition of hydrogen, have been investigated over nickel, cobalt and iron catalysts supported on 3-dimensional carbon fibre supports, using both a horizontal tube furnace and an isothermal, isobaric induction furnace. The transition metal catalysts were prepared by impregnating 3-dimensional carbon fibre supports with a methanolic solution of the metal nitrate, using a wet impregnation technique, and the effects of temperature, gas composition and deposition time on their catalytic behaviour was studied. Samples were characterised using a number of complementary techniques, including X-ray diffraction, scanning electron microscopy, polarised light microscopy, transmission electron microscopy, thermogravimetric analysis, digital photography and weight change measurements. The findings from these techniques were used to explain the observed type and amount of carbon deposited. Nickel was found to be the most active catalyst and methane was found to be a poor carbon precursor for the catalytic deposition of carbon, from these findings nickel was chosen as the catalyst and ethane and synthetic natural gas were used as the carbon precursors, with and without the addition of hydrogen. The activity of the nickel catalyst was found to be dependant on a number of factors; weight percent used, temperature, gas feedstock used and deposition time. It was found, in all cases, that increasing the deposition temperature resulted in higher deposition rates, ethane was found to yield higher deposition rates than synthetic natural gas and the effect of hydrogen addition had a negligible effect upon the rate of carbon deposition for the reactions carried out in ethane whereas it was significant for the reactions carried out in synthetic natural gas. The majority of the carbon deposition took place in the first three hours of deposition, with extended deposition times only yielding small increases in the overall rate of carbon deposition. The type of carbon deposited varied from filamentous carbon i.e. carbon nanotubes, nanofibres and microcoils, to encapsulation. The factors affecting the type of carbon deposited were, the temperature of carbon deposition, with higher temperatures (800C) yielding encapsulation and lower temperatures (650C) yielding filamentous carbon, and the addition of hydrogen, with higher hydrogen concentrations favouring the formation of filamentous carbon over encapsulation. It was also found that the addition of hydrogen did not extend the lifetime of the catalysts. It was found that nickel catalysts could be used within larger carbon fibre preforms to catalytically deposit carbon at lower temperatures than those used in industry for the manufacture of carbon-carbon composites (> 1000C).
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Li, Qiang. "Growth of carbon nanotubes on electrospun cellulose fibres for high performance supercapacitors and carbon fibre composites." Thesis, University of Exeter, 2018. http://hdl.handle.net/10871/34360.
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The production of cellulose derived hybrid carbon nanofibre (CNF)/carbon nanotubes (CNTs) electrodes for the fabrication of supercapacitors and carbon fibre composites was investigated. The CNTs were grown via a floating catalyst chemical vapor deposition (CVD) method on the top surface of electrospun cellulose derived CNFs. These CNF and CNF/CNTs samples were then used as electrodes to produce liquid electrolyte-based supercapacitors. The growth of CNTs leads to an improvement of electrochemical performance compared to the plain CNFs. This improvement is due to the grown CNTs enlarging the reactive sites through enhanced surface area and porosity, and thereby increasing the conductivity of the system. CNTs have been also grown onto CNFs containing ferrocene and SiC particles. Composites were fabricated by combining the fibres and CNTs grown fibres with model polymers. The stress transfer properties of these materials have been estimated using an in situ Raman spectroscopic method by observing the shift of the Raman band during the tensile deformation of model polymer composites. Using this method, the elastic modulus of CNF/SiC/CNTs fibres has been estimated to be 208 ± 26 GPa. No shifts in the peak positions of bands relating to the carbon structure were obtained for in situ Raman spectroscopic studies of the CNF/CNTs fibres made from the ferrocene embedded fibres. This was thought to be due to the low yield of CNTs on the surface of the fibres. Furthermore, CNF/CNTs electrode-based structural supercapacitors, combining a solid electrolyte with the carbonized fibres, have been produced. These CNF/CNTs electrodes have a better capacitive performance than the plain CNF electrodes. There was a decrease in this performance with increased curing time of the resin, from 2 to 24 h, due to a lack of charge carrier mobility in the latter samples. A Raman spectroscopic study of the deformation of the carbon structures showed that the G-band shift towards a lower wavenumber position for the CNF and CNF/CNTs samples processed at a carbonization temperature of 2000 °C. Moduli of these fibres were estimated to be ~145 GPa and ~271 GPa, respectively, suggesting the growth of CNTs not only enhances the capacitive performance but also the mechanical properties of the structural supercapacitors. No Raman bend shift was found for the CNFs and CNF/CNTs samples processed below a carbonization temperature of 2000 °C, e.g. 900 °C and 1500 °C. This is because the graphitic structures are not well developed at carbonization temperatures below 1500 °C.
7
Cantwell, W. J. "Impact damage in carbon fibre composites." Thesis, Imperial College London, 1986. http://hdl.handle.net/10044/1/7834.
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Kortschot, Mark Timothy. "Damage mechanics of carbon fibre composites." Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293010.
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Hawtin, Benjamin Charles. "Defect criticality of carbon fibre composites." Thesis, University of Bath, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.425875.
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Erland, Samuel. "Characterisation of uncured carbon fibre composites." Thesis, University of Bath, 2017. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.715265.
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The weight saving benefits of carbon fibre composites have been keenly adopted by civil aviation, with over 50% of the weight of modern designs coming from the carbon fibre components. The rapid rise in demand for this new material has led to the development of fully automated manufacturing techniques, improving rate of production and repeatability of manufacture. However, this rapid development, combined with a constant drive for increased rate of manufacture from industry can result in the formation of critical defects in the more complicated structural components. Manufacturing complex aeronautical structures from carbon fibre leads to a number of interesting mechanical problems. Forcing a multi-layered laminate to conform to a curved geometry requires individual layers to move relative to one another in order to relieve various forming-induced stresses. If the layers are constrained the dissipation of these stresses in the form of interply shear is prevented and a wide range of defects can occur, compromising the integrity of the final component. One of the most important of these is fibre wrinkling, which is effectively the buckling of one or more layers within an uncured laminate. This buckle results in a localised change in fibre orientation, which can result in a significant knockdown in part strength. A large amount of research has been conducted on carbon fibre in its cured state, when it exists as elastic fibres in an elastic matrix. Manufacturing occurs when the material is uncured however, with modern processes typically using fibres which are pre-impregnated with resin in order to reduce void content and aid fibre placement. A ply of uncured material therefore consists of stiff elastic fibres suspended in a very weak liquid viscoelastic material, whose properties are hugely influenced by temperature and rate of deformation. This thesis builds a better understanding of the mechanics involved in forming, using a series of characterisation techniques developed drawing from techniques in the literature. Part of the process involves the fitting of a one-dimensional viscoelasto-plastic model to experimental test data in order to represent the material response when shearing two plies about their interface. This model shows the material response to be dominated by the viscoelastic resin at low temperatures, before becoming frictional and fibre dominated at higher temperatures. In terms of optimum formability, a region exists in the transition from the viscous to frictional behaviour at which resistance to forming is minimised. With this data alone, optimum forming parameters such as rate of deformation, pressure and temperature can be suggested based on the material being used, along with design parameters such as stacking sequence. Another important characteristic which must be understood when considering ply wrinkling is the bending stiffness of uncured prepreg, both as a single ply and when combined to form a small laminate. A wrinkle is in effect the buckling of a single or small number of plies within a laminate, therefore by understanding the bending stiffness and process-induced loading we can begin to predict whether or not wrinkles are likely to occur for a particular manufacturing regime. In order to assess bending stiffness, a modified Dynamic Mechanical Analysis process is employed, replacing the standard Engineers Bending Theory calculations with a Timoshenko element to capture the large degree of intraply shear experienced in the bending of uncured prepreg. Finally, a small laminate scale demonstrator is considered in which a 24-ply laminate is consolidated into a female tool in such a way as to induced maximum shear strain between the plies, in order that the optimum forming parameters predicted by the characterisation tests might be validated. A simple energy minimisation model is used to predict the variation in consolidation strain around the part due to resistance to shear, using material parameters from the model describing the inter-ply shear test data. These parameters are also used to inform a novel modelling technique which has been developed parallel to this thesis, which is validated against the experimental results, and shows how the characterisation techniques can be used to advance simulation methods aimed at reducing the development time for new carbon fibre components. This work provides a set of tests and methodologies for the accurate characterisation of the behaviour of uncured carbon fibre during forming. The models developed alongside these tests allow for a detailed interrogation of the results, providing valuable insight into the mechanics behind the observed material behaviour and enabling informed decisions to be made regarding the forming process in order that the occurrence of defects might be minimised. The primary aim has been to provide a set of vital input parameters for novel, complex process modelling techniques under development, which has been achieved and validated experimentally.
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Lloyd, Rachel Louise. "Recycling of carbon fibre composite material." Thesis, Cranfield University, 2002. http://dspace.lib.cranfield.ac.uk/handle/1826/11356.
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Different routes for recycling carbon fibre composites from the aircraft industry were
investigated for feasibility., Literature analysis revealed little previous ·work in this area,
with most composite recycling investigations concentrating on automotive industry
wastes.
The magnitude of disposal of carbon fibre composite materials from the aircraft industry
is estimated to be in the region of 350,000 tonnes between the years 2000 and 2050.
Landfill cost investigations concluded that the corresponding disposal cost will be in the
region of £52 million. Experimentation indicated that the material was stable in landfill
conditions, whilst investigations into the health and safety aspects of composite
recycling revealed that the materials were harmless unless reduced diameter fibres were
released.
Activation experiments concluded that the production of commercially viable active
carbons was not possible - although the resins activated the carbon fibres did not.
Maximum BET surface areas of 170 m2 g-
1
were achieved, despite employing different
activation methods and pre-treatments.
Therefore, alternative recycling routes were investigated. Two brainstorming sessions
generated over forty options. After analysis for of these options were considered most
likely to succeed and were investigated in more depth. .
Fragment mitigation trials showed a significant reduction in fragment velocity (-20 %)
using composite plates of 10.5 mm thickness, liquid-holding boxes resulted in fragment
velocity reductions of up to 75 %. Delamination was localised to the area of impact.
Literature based investigations of fibre recovery methods identified fluidised bed and
high-pressure steam as the most likely to be viable, with fluidised bed plants breaking
even at throughputs under 9,000 t/yr. Chemical digestion and resin burn off produced
significantly weakened fibres, swelling resulted in the freeing of pre-preg layers.
Artificial reef investigations showed that although the material did not appear to
degrade in marine environments, it was unsuitable for organism growth. No organisms
were attached after a period of 1 year.
Pyrolysis appeared to be a viable option, with plants breaking even at throughputs of
approximately 6,000 t/yr.
Fragment mitigation, fluidised bed fibre recovery and pyrolysis were considered most
likely to offer technically and economically viable recycling 1"9utes, and it is
recommended that these routes should be investigated further.
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Shamsuddin, Siti Rosminah. "Carbon fibre reinforced poly(vinylidene fluoride)." Thesis, Imperial College London, 2012. http://hdl.handle.net/10044/1/9803.
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The demand for oil in the world is expected to rise by 1.7% in the fourth quarter of 2012 compared to fourth quarter of 2011. In order to cater for this increasing demand, the oil and gas industry continues to explore and develop deep-sea oilfields where oil and gas risers and pipelines encounter extreme conditions. The combination of high pressure and temperature with aggressive media which contains of hydrocarbon, alkanes, acids, sour gas (H2S), and CO2, etc., requires superior material performance and durability. Conventional engineering materials, such as steel are heavy and require corrosion protection, which are currently used as risers, flowlines and choke and kill lines have reached their limits. This is because of the poor chemical resistance and damage tolerance and the high costs involved in supporting their own weight. This has motivated the industry to explore non-corroding and lighter alternative materials if deeper sea reservoirs are to be explored. One such material that has the potential to overcome such limitations thus enabling new design strategies for cost effective, weight and energy saving materials is fibre reinforced composites. The remarkable properties and the tailorability of fibre reinforcement along load paths to achieve excellent performance of the composites is an attribute not found in any other material. The aim of this research was to manufacture novel carbon fibre reinforced polyvinylidene fluoride (PVDF) composites by incorporating atmospheric plasma fluorination of the carbon fibres. Powder impregnation method was adapted for the manufacturing of continuous unidirectional (UD) carbon fibre reinforced PVDF composite prepregs. The resulting composite laminates were characterised through various macro-mechanical tests. The impact of atmospheric plasma fluorination of the carbon fibre on the tensile, flexural, short beam shear and tearing properties of the UD composites were investigated to determine whether the improvements observed in the single fibre model composite can be translated to macro-level composite laminates. Apart from this, the impact of combining both fibre and matrix modifications on the composite were studied and the preliminary results on micro-mechanical scale are presented. Finally, composite pipe structures, made by filament winding technique using unidirectional carbon fibre reinforced PVDF composite prepregs onto a pure PVDF liner were fabricated, and characterised with respect to its mechanical properties.
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Zhang, Jing. "Différents traitements de surface des fibres de carbone et leur influence sur les propriétés à l'interface dans les composites fibres de carbone/résine époxyde." Thesis, Châtenay-Malabry, Ecole centrale de Paris, 2012. http://www.theses.fr/2012ECAP0038/document.
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Les matériaux composites à base de fibres de carbone (CF) sont actuellement très utilises dans le domaine de l’aérospatiale, de la construction et du sport grâce à leurs excellentes propriétés mécaniques, une faible densité et une haute stabilité thermique. Les propriétés des composites dépendent fortement de la nature et de la qualité de l’interface fibre/matrice. Une bonne adhérence interfaciale permet un meilleur transfert de charge entre la matrice et les fibres. Les CFs sans traitement sont chimiquement inertes et présentent donc une faible adhérence vis-à-vis de la résine époxyde. Par ailleurs, les faibles propriétés transversales et interlaminaires limitent sensiblement la performance et la durée de vie des composites. Par conséquent, un type de renfort à base de fibres traitées est fortement souhaité pour améliorer les propriétés globales des composites, en particulier l'adhésion interfaciale entre les fibres et la matrice. Dans cette thèse, trois types de traitement de surface, l’ensimage, le traitement thermique et la croissance de nanotubes (CNTs), ont été appliqués aux CFs. En particulier, les CFs greffées de CNTs, se combinant avec les deux autres traitements, montrent la meilleure adhérence interfaciale avec la matrice époxyde. L’ensimage proposé peut améliorer la performance du CNT-CF hybride et minimiser les dommages aux fibres lors de la manipulation ultérieure tels que le transport et la préparation de composites. Tout d’abord, l’ensimage a été réalisé sur la surface des fibres par dépôt de résine époxyde en solution. L’ensimage permet de protéger les filaments au cours de la mise en oeuvre et favorise également la liaison fibre/matrice. Différentes formulations d’ensimage selon les proportions époxy/durcisseur ont été utilisées. La quantité d'ensimage déposée sur les fibres de carbone a été contrôlée en faisant varier la concentration de la solution d’ensimage. Ensuite, un traitement thermique, effectué sous un mélange de gaz à 600-750 oC, a permis de modifier la surface des CFs. L'influence de la composition du gaz, du temps de traitement et de la température sur les propriétés interfaciales des composites CFs/époxy a été systématiquement quantifiée. Enfin, des CNTs ont été greffés sur les CFs par une méthode de dépôt chimique en phase vapeur en continu afin d’obtenir un nouveau type de renfort hybride multi-échelle. Les CNTs greffés permettent d’augmenter la surface de contact et d’améliorer l’accrochage mécanique de la fibre avec la résine. De plus, ils pourraient améliorer la résistance au délaminage, les propriétés électriques et thermiques des composites. Les CFs greffées de CNTs de différentes morphologies et densités ont été produites en faisant varier les conditions de croissance. Après le traitement de surface, les essais de fragmentation ont été menés afin d’évaluer la résistance au cisaillement interfacial (IFSS) des composites CFs/époxy. Par rapport aux fibres vierges, l’ensimage et le traitement thermique ont contribué à une augmentation de l'IFSS de 35% et de 75%, respectivement. L'adhésion interfaciale entre la matrice époxyde et les fibres greffées avec CNTs pourrait être adaptée en faisant varier la morphologie, la densité de nombre et la longueur de CNT. Les CFs greffées avec 2% en masse de CNTs (10nm de diamètre) ont entraîné une amélioration de l'IFSS de 60%. Un traitement thermique et un ensimage pourraient contribuer à une augmentation supplémentaire de 108%. Il convient de mentionner que la dégradation des fibres n’a pas été observée après les divers traitements précédemment évoqués. Les résultats de ces travaux pourraient mener au développement de ces techniques à plus grande échelle pour la conception de structures à base de composites CFs/époxyCarbon fiber (CF)-reinforced polymer composites are widely used in aerospace, construction and sporting goods due to their outstanding mechanical properties, light weight and high thermal stabilities. Their overall performance significantly depends on the quality of the fiber-matrix interface. A good interfacial adhesion provides efficient load transfer between matrix and fiber. Unfortunately, untreated CFs normally are extremely inert and have poor adhesion to resin matrices. Meanwhile, poor transverse and interlaminar properties greatly limit the composite performance and service life. Therefore, a new kind of fiber-based reinforcement is highly desired to improve the overall composite properties, especially the interfacial adhesion between fiber and matrix. In this thesis, three kinds of surface treatment, including sizing, heat treatment and carbon nanotube (CNT) growth, were applied to CFs. In particular, CFs grafted with CNTs, combining with the other two treatments demonstrate superior interfacial adhesion to the tested epoxy matrix. The proposed epoxy sizing can improve the CNT-CF hybrid performance and prevent fiber damage during the subsequent handling such as transport and composite preparation. Firstly, epoxy-based sizing was applied onto the CF surface by the deposition from polymer solutions. Sizing could not only protect the carbon fiber surface from damage during processing but also improve their wettability to polymer matrix. A detailed study was conducted on the influence of the ratio of epoxy and amine curing agent in the sizing formulation. The sizing level on the fiber surface was controlled by varying the concentration of polymer solutions. Secondly, heat treatment in a gas mixture at 600-750 oC was used to modify the carbon fiber surface. The effect of gas mixture composition, treatment time and temperature on the interface was evaluated systematically. Thirdly, CNTs were in-situ grafted on the carbon fiber surface by a continuous chemical vapour deposition (CVD) process to obtain hierarchical reinforcement structures. These hybrid structures have the potential to improve the interfacial strength of fiber/epoxy composites due to the increased lateral support of the load-bearing fibers. Meanwhile, the CNT reinforcement could improve the composite delamination resistance, electrical and thermal properties. The CF grown with CNTs of different morphologies and densities were produced by varying CVD conditions. After the surface treatment, single fiber fragmentation test was used to assess the interfacial shear strength (IFSS) of carbon fiber/epoxy composites. Compared with the as-received CFs, the epoxy sizing and the heat treatment contributed to an improvement in IFSS of up to 35% and 75%, respectively. The interfacial adhesion between epoxy matrix and CNT-grafted fibers could be tailored by varying the CNT morphology, number density and length. The CFs grafted with 2 wt% CNTs of 10 nm in diameter resulted in an improvement in IFSS of around 60%. A further heat treatment and epoxy sizing could contribute to an additional increase of 108%. It’s worth to mention that no significant strength degradation of the fibers was observed after the surface treatments. This work could support the development of large-scale approach to CF surface treatment, and throw light on the design of structurally efficient CF/epoxy composites
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Broughton, William Richard. "Shear properties of unidirectional carbon fibre composites." Thesis, University of Cambridge, 1990. https://www.repository.cam.ac.uk/handle/1810/250965.
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Otunga, Moses Gerishom. "Fatigue damage accumulation in carbon fibre laminates." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389888.
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Harper, Lee Thomas. "Discontinuous carbon fibre composites for automotive applications." Thesis, University of Nottingham, 2006. http://eprints.nottingham.ac.uk/10246/.
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Increasingly stringent emissions targets are encouraging vehicle manufacturers to prioritise reduction of vehicle mass. The falling cost of carbon fibre is increasing the viability of lightweight carbon-based body panel systems across a broad range of production volumes. In the present work an automated process has been developed for the manufacture of random fibre preforms at medium volume production levels (30-50,000ppa). This thesis seeks to understand the influence of key microstructural parameters on the mechanical and physical properties of carbon fibre laminates produced by directed fibre preforming. The principal parameters studied are fibre length, tow filament count and laminate thickness. A statistical process simulation has been developed to predict preform density variation and the results are compared with experimental tensile properties. Experimental studies have shown that there is a notable reduction in areal density variation and consequently an increase in tensile properties with shorter fibres (115mm to 6mm) and thicker laminates (1.5mm to 4mm for a constant volume fraction). Shorter lengths improved preform coverage and gave higher tensile strength, whilst thicker laminates reduced the presence of unreinforced areas which cause stress concentrations. Tow filamentisation has been induced by pneumatic means to reduce the mean filament count and maximise the mechanical performance when using inexpensive, 24K bundles. By maximising the level of filamentisation both stiffness and strength can be increased by 20% and 45% respectively. An analytical stiffness model is presented to predict the effect of tow filament count on the in-plane elastic constants. Filament count and out-of-plane fibre orientation distributions are determined from optical microscopy and are incorporated into a multi-level Mori-Tanaka based model. Predictions are within 8% of the experimental data for laminates containing large fibre bundles and 10% for laminates with highly filamentised bundles. An expression for critical bundle length has been developed for more accurate strength prediction, based on the number of filaments within the bundle. Experimental results confirm that the critical tow length is proportional to the tow filament count. Directed fibre preforming has been benchmarked against other competing processes in respect of mechanical properties, weight saving potential and cost. A full-scale demonstrator component has been manufactured using a variety of carbon composite solutions, which can all provide 40 to 50% weight saving for an equivalent bending stiffness to steel and greatly improved dent resistance. Directed fibre preforming has shown great promise for both semi-structural and structural components for medium volume applications, particularly when aligned fibres are introduced. The results from this work can be directly scaled for industrial application to provide a cost effective, lightweight alternative to steel.
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Kanellopoulos, V. N. "Hygrothermal characteristics of carbon fibre reinforced plastics." Thesis, University of Salford, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356171.
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Jennings, Tracy Michelle. "Thermal fatigue of carbon fibre-bismaleimide composites." Thesis, University of Cambridge, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.290903.
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Spearing, Simon Mark. "Fatigue damage mechanics of carbon fibre laminates." Thesis, University of Cambridge, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305821.
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Bullegas, Gianmaria. "Carbon fibre laminates with engineered fracture behaviour." Thesis, Imperial College London, 2017. http://hdl.handle.net/10044/1/56618.
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A new bio-inspired microstructure design approach was developed to improve the translaminar toughness and damage tolerance of Carbon Fibre Reinforced Plastic (CFRP) structures. The microstructure designs take inspiration from the microstructures of biological composites by adopting the most important toughening mechanisms, and applying them to CFRP laminates. Carefully placed patterns of laser-engraved micro-cuts are inserted in the microstructure of the laminate during the manufacturing process. These micro-cuts change the crack propagation path during translaminar fracture, hence allowing to engineer the fracture behaviour of the composite. The microstructure design approach led to remarkable improvements in the maximum tensile load (up to 189%) and translaminar work of fracture (up to 460%) during Compact Tension test for CFRP laminates with Cross-Ply and Quasi-Isotropic (QI) layups when compared with the corresponding un-modified laminates. Furthermore, a significant improvement in the damage resistance under indentation test was demonstrated for a QI laminate with engineered microstructure. These results demonstrate that microstructure design holds the potential to improve the damage tolerance of CFRP structures in industrially-relevant applications. A semi-analytical Fibre Bundle Model (FBM) was developed to investigate the role of dynamic stress concentrations, and of fracture mechanics-driven failure, on the longitudinal tensile strength of fibre-reinforced composites. In particular, the investigation was focused on the size effect: a decrease in the bundle strength with an increase in the number of fibres. To the knowledge of the author, it is the first attempt in the literature to investigate these two physical mechanisms in a FBM. It was shown that, although the dynamic stress concentrations significantly decrease the predicted bundle strength, do not allow to predict the right trend of the size effect shown by the experimental results. On the contrary, including fracture mechanics-driven failure in the bundle simulation allowed to predict the right trend of the size effects on the bundle strength. These results suggest that fracture mechanics is a physical mechanism which might be necessary to consider to correctly predict the longitudinal tensile strength in large composite bundles.
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Shyha, Islam Saad Elsayed Mohamed. "Drilling of carbon fibre reinforced plastic composites." Thesis, University of Birmingham, 2010. http://etheses.bham.ac.uk//id/eprint/1353/.
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Following an extensive literature survey focusing on the machinability of carbon fibre reinforced plastics (CFRP), three main phases of experimental work were undertaken to evaluate the drilling of CFRP and associated stack materials. Phase 1 and 2 involved small diameter holes (1.5 mm) in thin CFRP laminates (3 mm thick) while Phase 3 addressed the feasibility of one-shot drilling (6.35 mm diameter holes) in multilayer workpiece stacks comprising titanium, CFRP and aluminium. Machinability was assessed in terms of tool life/wear, force/torque, hole size and geometrical accuracy, workpiece surface integrity and chip morphology.
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Potgieter, Cornelis Marthinus. "Rapid tooling for carbon fibre compression moulding." Thesis, [Bloemfontein?] : Central University of Technology, Free State, 2014. http://hdl.handle.net/11462/125.
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Thesis (M. Tech.) -- Central University of Technology, Free State, 2010The aim of this study is to produce more cost effective carbon fibre (CF) parts. To achieve this there must be a saving on materials, labour and time. Thus, a production process to produce cost effective CF moulds while saving time and money is required. This procedure must be suited for the incorporation in the small to medium production ranges. The composite industry is one of the fastest growing industries in the world. Therefore, the faster a mould can be produced, the faster the end product will reach the market. This research project investigates the possibility to sinter CF moulds on the Electro Optical Systems (EOS) Laser Sintering (LS) machine cheaper and faster than the conventional method using computer numerically controlled (CNC) machining. The surface finish produced on the LS machine is not of the same quality as a CNC machined mould, but there are ways to enhance the surface quality of a LS part to the point that it is compatible to the surface quality of a CNC machined mould. The CF moulding process uses many different types of moulding processes. However, it is not possible to use LS parts for all of the available processes to produce CF parts. In this study only one CF moulding process will be investigated, namely compression moulding. The moulds will be designed to be manufactured as cheaply and as quickly as possible. Different methods of mould adapting have been studied to find the cheapest most suitable method of mould design for the LS process.
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Qian, Connie Cheng. "Structural optimisation of discontinuous carbon fibre composites." Thesis, University of Nottingham, 2014. http://eprints.nottingham.ac.uk/14542/.
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There has been a growing interest in using discontinuous carbon fibre composites for semi-structural applications within the automotive industry. The main advantages of discontinuous fibres are low material costs, low wastage and low touch labour compared with processes using carbon fibre textiles. Directed Carbon Fibre Preforming (DCFP) is an automated process for producing complex 3D preforms for liquid moulding. DCFP offers the potential for producing highly optimised structures, with local control over tow size, fibre length and volume fraction within the component. The execution of this is challenging however, as confidence in the current library of material properties is low and existing structural optimisation packages only consider a very limited number of design variables, which are restricted to more conventional composite materials. This thesis aims to establish a structural design tool to exploit the design freedom offered by the DCFP process. A large number of parameters associated with the fibre architecture can be controlled to meet a range of design criterions such as performance, weight and cost. The optimisation tool is capable of generating locally varied fibre areal mass and thickness maps that are suitable for manufacture by the robot controlled process. The developed model adopts a multi-scaled finite element approach. Meso-scale simulations are performed to establish size effects in discontinuous fibre composites, to quantify the level of stochastic variability and to determine the representative volume element for a given fibre architecture. A DCFP material database is generated to facilitate macro-scale modelling at the component level. The macro-scale model iteratively redistributes material in order to minimise the total strain energy of the model under prescribed loading conditions. The optimised model is segmented into areas of uniform areal mass, where the zone geometries are tailored to achieve representative material properties according to the meso-scale results, whilst ensuring the design is fit for manufacture. An automotive spare wheel well has been chosen as a demonstrator component, enabling two DCFP architectures to be compared against a continuous glass/carbon fibre NCF design. The first case offers a high performance (high specific stiffness) solution and the second offers a low cost option using high filament count tows. Following optimisation, results suggest that a 3K 25mm fibre length DCFP option can achieve a specific stiffness 52% higher than the glass/carbon baseline design, but for 1.33 times higher material cost. Alternatively, the specific stiffness of a 24K 50mm fibre length DCFP is marginally lower than the first option, but still out-performs the baseline for just 67% of the material cost. The structural optimisation method demonstrates that discontinuous fibre composites can compete against continuous fibre counterparts for semi-structural applications.
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Koncherry, Vivek. "Multifunctional carbon fibre flat tape for composites." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/multifunctional-carbon-fibre-flat-tape-for-composites(24dc2fc9-0649-41c5-8db2-7121cf16126b).html.
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Recently, there has been a significant growth in the use of composites in sectors such as automotive, aerospace and wind energy. Composites are traditionally designed for mechanical performance in terms of strength, stiffness and impact energy absorption; however multifunctionality has become the focus of researchers and designers in recent years. Multifunctional design of composites involve adding functionality such as thermal management, radiation shielding, stealth, structural health monitoring and energy storage at material level rather than adding discrete components afterwards. The aim of the current research is to incorporate multi-functionality at tow-scale both as a processing aid during manufacture and adding additional functionality during subsequent processing. Various laboratory scale machines were developed as a part of this study to identify the ideal way to spread and incorporate metallic materials into the carbon fibre tows, thereby making them multifunctional. Manufacturing processes such as co-mingling of micro-fibres, coating with metallic powder and screen printing of metallic grid lines have been developed in this work. One of the objective of this thesis is to metallise carbon tow in order to use it in conjunction with magnetic tooling, as part of the chopped fibre preforming process developed by the University of Nottingham and Bentley Motors. The performance of the metallised tow has been evaluated using characterisation tests such as magnetic pull force test, bending rigidity test etc. Finite element models have been developed to verify the experimental results of magnetic pull force and bending properties. As observed during the research, the bending properties of the carbon tow were found to influence the accuracy of the finite element modelling significantly. Study into the bending properties of the carbon fibre and Multifunctional carbon tow using two different principles such as carbon tow bending under own weight and bending due to the application of an external force were carried out. In each case the governing mathematical models were also derived.
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Riaz, Sheema. "Carbon fibre reinforced PVDF and PEEK nanocomposites." Thesis, Imperial College London, 2012. http://hdl.handle.net/10044/1/9502.
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There is currently a well-timed opportunity to create intensely improved structural materials to be used as risers in the offshore oil and gas industry where high mechanical performance along with superior resistance to chemical attack is required. Recent evidence shows that carbon nanotubes (CNTs) are the ideal reinforcement for polymer fine structures and are expected to improve the matrix modulus, which should lead to composites with much improved compression and other matrix dominated properties. By combining conventional reinforcing fibres and CNTs within thermoplastic matrices, a new class of materials with both superior mechanical, environmental, and chemical performance, as well as significantly reduced through-life costs should be possible. Different formulations of nanocomposites consisting of modified Polyvinylidene difluoride (PVDF) and modified CNTs e.g. Poly methyl methacrylate grafted carbon nanotubes (PMMA-g-CNTs) were fabricated using extrusion and injection moulding up to a maximum CNT content of 10 wt%. CNTs were well distributed within polymers as determined through optical and electron microscopy. Dynamic mechanical analysis was conducted in order to study the effect of CNTs on storage modulus of nanocomposites. The tensile, flexure and compression properties of PVDF nanocomposites were increased with increase in CNT content. Overall, PMMA-g-CNTs based PVDF nanocomposites with a 10 wt% CNT loading showed 20%, 30% and 60% improvement in tensile, compressive and flexural modulus as compared to PVDF nanocomposite containing 10 wt% CNT loading. The main objective of this research was to optimise processing conditions for fabricating ultra-inert hierarchical fibre reinforced nanocomposites. The CNT modified matrix, prepared by solution precipitation, was reinforced with carbon fibres via continuous composite line setup to manufacture hierarchical reinforced thermoplastic (Polyvinylene difluoride (PVDF) and Poly ether ether ketone (PEEK)) composites. Thermoplastic hierarchical composites containing up to 1.25 wt% CNTs demonstrated improved compression and interlaminar shear strength whereas a decrease was observed of the same when CNT content was increased up to 5 wt%. A similar trend of decline in mechanical performance at higher loadings of CNTs (>1 wt%) was observed in PEEK based hierarchical composites which indicated that matrix dominated properties were availed without compromising the quality of fibre/matrix interface at an optimum loading of CNTs (1.25 wt%) resulting in enhanced mechanical performance of hierarchical composites. However, further addition of CNTs adversely effected the fibre impregnation by nanocomposite matrix, due to processing issues such as high viscosity of nanocomposites at higher CNT contents, resulting in poor mechanical performance. Moreover, the influence of CNTs on the fracture toughness was also investigated by double cantilever beam testing. Polished cross sections of fracture surfaces of failed composites were analysed to understand how CNTs affected the damage mode. Fractographic analysis of compression and double cantilever beam (DCB) failed PVDF and PEEK hierarchical composites also showed the presence of bare/dry fibres which indicates that nanocomposite's infusion/impregnation in to carbon fibres is being compromised at higher CNT loadings.
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Anthony, David Benbow. "Improved synthesis of carbon nanotube grafted carbon fibre : towards continuous production." Thesis, Imperial College London, 2012. http://hdl.handle.net/10044/1/39371.
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Grafting carbon nanotubes (CNTs) onto reinforcing fibre surfaces has been shown to improve composite structural performance, through improved interfacial bonding of the matrix and reinforcement. Sourcing a suitable amount of CNT-grafted fibre has currently limited test coupons geometry and development in the area. The scale-up of current synthesis procedures for grafting CNTs onto carbon fibre (CF) surfaces, using low intensity processing techniques (minimal processing of fibre substrate) compatible with industrial practices has not yet been reported. CNT growth from CF surface (CNT-g-CF) without damaging the mechanical parent fibre properties is a challenge as chemical vapour deposition (CVD) CNT growth typically results in catalyst pitting and surface defects occurring. In this thesis I attempt to address concerns detailed above; through the development of a catalyst system which is easily deposited onto CF, uses a CVD CNT-synthesis method which does not damage the original fibre properties in a potentially continuous scalable manner. I present a simple incipient wetness technique for loading a bi-catalyst precursor mixture onto CF. CF pre-deposited with bi-catalyst precursor under the application of an electric field, using CF as an electrode, in-situ during conventional thermal-CVD demonstrated significant promotion of CNT-synthesis directly from the CF surface. Electric field applied during CVD CNT-synthesis produces CNT-g-CF without apparent mechanical degradation to the parent fibre retaining original mechanical properties. When CVD CNT-synthesis is undertaken without the application of an electric field, degradation of original mechanical properties are witnessed. Batch CVD process was adapted, in an attempt to demonstrate the feasibility of continuous production of CNT-g-CF in a bespoke continuous CVD set-up. Alternative routes for CNT-g-CF including a novel silicon oxide based CNT-synthesis are also discussed.
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Pardini, Luiz Claudio. "The structure & properties of SiC-modified carbon fibre reinforced carbon composites." Thesis, University of Bath, 1994. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359217.
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Rose, Ansgar. "Fibre-matrix interactions in reinforced thermoplastics." Thesis, Brunel University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362402.
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Yan, Ying. "Finite element analysis and characterisation of fibre and fabric reinforced composites." Thesis, University of Ulster, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385688.
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Constantin, Hannah. "Carbon fibre reinforced aluminium for lightweight vehicle structures." Thesis, University of Nottingham, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.718465.
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The impact of human activity on the environment is significant. One way to reduce our carbon footprint is to decrease the mass of passenger vehicles, improving fuel efficiency. In addition, the use of recycled materials can reduce environmental impact further. The aim of this project is to fabricate and evaluate novel recycled carbon fibre reinforced aluminium as a lightweight material for passenger vehicles. Recycled carbon fibre reinforced aluminium materials were fabricated by gas pressure infiltration. The infiltration behaviour of the preforms was quantified by mercury intrusion porosity, compared to other preform types, and compared to composite materials fabricated at different pressures. Recycled carbon fibre reinforced aluminium materials can be fabricated by gas pressure infiltration, using less than 12 bar gas pressure, resulting in fibres occupying approximately 11% of the material volume. A sodium silicate binder was utilised in an effort to increase the fibre packing fraction and improve preform handle-ability. Silicon was added to the aluminium matrix to inhibit the formation of aluminium carbide during fabrication at the fibre/matrix interface. Although this was not successful, the composite materials containing silicon exhibited reduced porosity and fibre breakage, and no aluminium carbide was observed after up to 4 hours of heat treatment. Nickel-coated carbon fibre was used to improve the wetting behaviour between the fibres and the matrix, which reduced the required pressure for infiltration with aluminium by five times. The mechanical properties of the composite material were evaluated using wear testing and a novel small-specimen creep test. The testing specimen size may not be representative of the composite material as a whole, as in most cases, the addition of carbon fibres had a deleterious effect on the mechanical properties of the material.
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Symons, Digby Duncan. "Impact damage tolerance of carbon fibre reinforced plastics." Thesis, University of Oxford, 1998. https://ora.ox.ac.uk/objects/uuid:1db49475-ac42-4259-91aa-b84ee6718875.
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Carbon fibre reinforced plastic (CFRP) is a composite composed of very high strength and stiffness carbon fibres within a polymer matrix. Low mass and cost make CFRP attractive for aerospace applications. At present application of CFRP is limited by the poor residual strength and fatigue properties of the material following impact damage, and because of the limited understanding of the problem. Damage to CFRP results in a combination of fibre fracture and matrix cracking. The strength of CFRP perpendicular to the fibre direction is relatively poor and so the material is generally used as a laminate of unidirectional plies of different fibre orientations. Laminates are particularly prone to delamination, this is matrix cracking which separates plies. In this thesis techniques for measurement of damage type and severity in CFRP are evaluated. These are used to quantify the distribution of damage resulting from hard body impacts at high, low and quasi-static incident velocities. A composite material damage model in a dynamic finite element analysis computer program (DYNA 3D) was used to predict the experimentally measured impact damage. However the prediction was found to be insufficiently accurate for reliable use by designers. Recommendations are made for improvements in the numerical modelling of impact damage in CFRP. Mechanical tests that provide data on the effect of impact damage on the residual strength of CFRP specimens are reported. These show that providing impact damage is limited to delamination, with little fibre fracture ocurring, the compressive residual strength will be more severely reduced than the tensile property. Strain gauge measurements show that this effect is caused by local compressive buckling of the delaminated plies in the impact damaged area. Lquivalent hole sizes, causing the same residual strengths as in the impact damaged specimens, are given. Cyclic load tests were conducted providing stress-life data for impact damaged specimens of CFRP. The data fit a stress-life diagram divided into three scatter band regions: static fracture; cycle dependent damage growth; and infinite life. Qualitative and quantitative observations are given of the progression of damage in a fatigue after impact damage test. Strain gauge and force/extension measurements show the presence of creep and energy absorption in undamaged and impact damaged CFRP. Much of the observed behaviour may be explained by a viscoelastic model. Because of the presence of viscoelastic creep it is suggested that the fatigue mechanism must depend on interacting cycle dependent and time dependent mechanisms.
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Chen, Ping. "Interfacial degradation of carbon fibre reinforced polyetheretherketone, PEEK." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ29373.pdf.
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Dyson, Igor Niladri. "The fracture behaviour of carbon fibre/polyetheretherketone composites." Thesis, Imperial College London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.309100.
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Gu, Xiaohong. "Micromechanics of model carbon-fibre/epoxy-resin composites." Thesis, University of Manchester, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.488261.
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Kuzjatkin, Juri. "Structural Weight Optimisation of a Carbon Fibre Ferry." Thesis, KTH, Marina system, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-163696.
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The Damen Ferry department is developing a concept of fast ferries (DFFe) built of composite materials. Based on the previous experience in composite shipbuilding of Damen modular waterbuses (DWBu) and Water Taxies the Ferry department tries to utilize the existing experience and use it in production of larger vessels that are capable to develop higher speeds and carry more passengers. The key objective is the weight saving - that results in a lighter and therefore more sustainable craft that consumes less fuel and is capable to carry more payload. The expectations are at least 30 per cent of weight saving comparing to the aluminium version of the craft. A general structural plan of the vessel is the basis of this thesis. The structural design is as much as possible defined based on the regulations according to classification society Det Norske Veritas. Three global load cases are considered: longitudinal bending, transverse bending and torsional bending. Besides, five local load cases are considered: sea pressure on the hull, impact pressure on the bottom of the hull, wet deck slamming, deck loads and superstructure loads. Lightweight is one of the important reasons to develop the vessel in composite materials. The material combination of carbon fibre (CF) and vinyl ester (VE) resin is chosen for this vessel. This combination of materials has superior mechanical properties but is considered relatively expensive comparing with glass fibre (GF). The preference is given to CF due to its high strength-to-weight and stiffness-to-weight ratios, which give possibility to obtain the same strength and higher stiffness with lower weight and better mechanical properties than GF. All structural members except the wheelhouse that is not included in this thesis will be sandwich construction because of the much increased strength and stiffness regarding weight. As core material cross-linked PVC will be used. The vessel will be produced with vacuum infusion, which enables relatively fast production and ensures good and consistent material properties. The material properties and safety factors for strength are determined according to Bureau Veritas. Robustness of the laminates is defined by describing minimum laminate thicknesses. Based on the analytical considerations and design requirements a set of optimisation tools has been developed to optimise various composite structures in order to achieve a lightweight solution for the composite craft. The approach used for the development of the tools is fully analytical and can be called as Simple FEA Approach giving the possibility to mesh the analysed structural members in order to get a full picture of the responses due to the applied loads. The developed tools are relatively easy to handle, yet some knowledge in composite structures is needed in order to be able to give critical judgement upon the design of the craft. The tools can be used not only for the preliminary design of the craft and weight estimation needed for the proposal documents provided to the client but also for later design stages when the final scantlings of the craft are estimated. The validation of the developed tools and global analysis of the vessel is performed using Siemens NX. A CAD model is created and linked to a Finite Element environment where different load cases can be evaluated. Adjustments of the material definition could be necessary depending on the results of the Finite Element Analysis.
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Al-Hazmi, Farag Saeed. "High strain rate behaviour of carbon fibre composites." Thesis, Loughborough University, 1995. https://dspace.lboro.ac.uk/2134/14116.
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This thesis describes a study of the dynamic mechanical properties of two types of carbon fibre composite: IM7/977-2 with 977-2 toughened thermoset resin, and IM7/APC2 with thermoplastic PEEK resin, both using Hercules IM7 carbon fibres with a volume fraction of 62%. The Split Hopkinson Pressure Bar (SHPB) is used to produce dynamic strain rates ranging from 10³ to 5x10³s⁻¹, while Instron and Hounsfield screw driven machines are used to give a constant strain rate of about 2 x 10⁻³s⁻¹ for comparative quasi-static loading. The Split Hopkinson Pressure Bar (SHPB) technique uses specimens in the form of a cylinder, sandwiched between two maraging steel bars. One of the maraging steel bars is subjected to an impact produced by a projectile. The Instron and Hounsfield machine used the same form of specimen. A strain gauge method has also been used to record the strain directly by attaching a strain gauge on to the specimen under test. Three different fibre orientations have been investigated: unidirectional fibre with loading parallel (0°) to the axis of the specimen; transverse loading (90°) where the fibres are perpendicular to the axis of specimen; and quasi-isotropic with transverse loading . The dynamic stress-strain properties of the carbon fib~e composites have been investigated experimentally at room temperature under quasistatic condition and at the high strain rates produced in the SHPB method using loading pulses of about 100 μS duration and rise time of 12 μS. The effects of strain rate on stiffness, yield stress and strength for the composites have been determined and compared with those obtained from a mathematical model (Rule of Mixtures). The longitudinal carbon fibre composite had the highest stiffness, followed by the quasi-isotropic composite, and then the transverse composite. For compressive strength, the quasi-isotropic had the highest strength followed by the longitudinal and then the transverse. The fracture energy has also been obtained indicating that for the quasi-isotropic composites, IM7/977-2 has a considerably high fracture energy than IM7/APC2. The bulk temperature rise has also been predicted up to the fracture stress.
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Lightfoot, James S. "Mechanisms of defect formation in carbon fibre composites." Thesis, University of Bristol, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.619140.
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Defects in composite materials lead to reductions in the mechanical performance of components. The presence of fibre waviness and through-thickness ply wrinkles has been shown to reduce the Compressive strength of laminates, and are therefore subject to significant scrutiny in the aerospace industry. Whilst a large volume of industrial effort and published research has addressed the reduction of the compressive strength Due to defects, the source of such defects is currently not well understood. The work presented in this thesis aims to elucidate the source of fibre waviness and ply wrinkles. Its ultimate goal is to understand the link between material and manufacturing process variations with the formation of such defects. Once mechanisms for defect generation are understood, measures can be taken by industrial manufacturers to mitigate their formation. As a result, part acceptance rates will increase; the composites industry depends on the reliability of component manufacture. A number of themes have been investigated by proposing specific mechanisms for the formation of fibre waviness and Ply wrinkles. Such themes include fibre-matrix interaction, tool part interaction and consideration. The most significant mechanism Has been shown to be consolidation. In both prepreg and woven preform materials, poor layup has been shown to lead to severe Ply bridging at tooling radii.
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Clarke, Howard W. J. "Reinforcing wrought iron with carbon fibre reinforced polymers." Thesis, University of Southampton, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.438037.
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Soutis, Constantinos. "Compressive failure of notched carbon fibre-epoxy panels." Thesis, University of Cambridge, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333387.
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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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Diao, Hele. "Carbon fibre reinforced polymer composites with enhanced ductility." Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/44273.
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Carbon fibre reinforced polymers (CFRPs) have high strength and stiffness, low density, long fatigue life in the fibre direction and good corrosion resistance. Nowadays, CFRPs are been used in aeronautics, wind turbine blades, sports goods and civil industry. However, one fundamental limitation of CFRPs is their brittleness (low ductility): CFRPs fail catastrophically at a relatively low strain (1.5% to 1.8%) under the tension with little warning or residual load-carrying capacity. To overcome this weakness, there is considerable interest to enhance the ductility of CFRPs exhibiting increased failure strains under tension and more progressive, graceful failure modes. In this work, three different methods were developed to improve the ductility of unidirectional (UD) CFRPs. The first method was to introduce fibre waviness into UD composites. The fibre alignment angles of the resulting composites and control composites were assessed and it was found that fibre waviness in UD composite did result in a stepwise tensile failure mode and an enhanced strain to failure. The second method was using an air-assisted fibre tow spreading and commingling technology to manufacture continuous intermingled carbon fibre/glass fibre hybrid tows. After defining and quantifying the degree of hybridisation (at the filament level) of two carbon fibre/glass fibre hybrid tows, the one with the higher degree of hybridisation was selected to manufacture intermingled UD hybrid composites. It was found that hybridising of continuous glass and carbon fibres resulted in the composites with an increased failure strain. Moreover, these hybrid composites failed more gradually. The final method investigated for introducing ductility was the introduction of ply cuts into PEEK interleaved UD carbon fibre/PEEK composites, which were manufactured by compression moulding. The resulting cut-ply interleaved carbon fibre/PEEK composite possessed a non-linear tensile stress-strain curve and ductility strain of 0.4%, which is due to shearing of the PEEK interleaves in the overlap regions between the cut carbon fibre plies.
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Makhdum, Farrukh. "Ultrasonically-assisted drilling of carbon fibre-reinforced plastics." Thesis, Loughborough University, 2014. https://dspace.lboro.ac.uk/2134/14721.
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Carbon fibre-reinforced plastics (CFRP) are widely used in aerospace, automobile and other structural applications due to their superior mechanical and physical properties. CFRP outperform conventional metals in high strength-to-weight ratio. Usually, CFRP parts are manufactured near to net-shape;however,machining is unavoidable when it comes to assembly. Drilling the holes are essential to facilitate riveting and bolting of the components. However, conventional drilling (CD) induces different types of damages such as cracking, fibre pull-out, sprintling and delamination due to the abrasive nature, inhomogeneity and anisotropy of CFRP. A novel technique, ultrasonically-assisted drilling (UAD) is hybrid machining technique in which highfrequency (typically above 20 kHz) vibration are superimposed on a standard twist drill bit in axial direction using ultrasonic transducer. UAD has shown several advantages such as thrust force reduction, improving surface quality and lower bur-formation in drilling of conventional metals. UAD has also effectively been used for drilling brittle materials.
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Kakemi, Manabu. "Hybrid continuous fibre cement composites." Thesis, University of Surrey, 1997. http://epubs.surrey.ac.uk/606/.
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Cartié, Denis D. R. "Effect of Z-fibres™ on the delamination behaviour of carbon-fibre/epoxy laminates." Thesis, Cranfield University, 2000. http://dspace.lib.cranfield.ac.uk/handle/1826/3293.
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The study presented in this thesis investigates the relationship between the experimentally determined behaviour of Z-pinned laminates under various delamination fracture loading conditions and their mesostructure Mode I, mode II and mixed mode 1/11 delamination fracture testing was carned out on Z-Fibre reinforced unidirectional beams of IMS/924 laminates For the Double Cantilever Beam specimens (DCB) under mode I loading, the crack propagation resistance of the beam is enhanced with increased pinning density For the range of pin diameters and pmmng densities used for this study, the load carrying capability has been improved by up to 5 times and the apparent toughness has been improved by up to 20 times The most noteworthy example of the effectiveness of ZFibreTM pinning is the stabilisation of delamination crack propagation under mode II loading conditions in the intrinsically unstable 3pt-ENF configuration Although the current data analyses, based on LEFM, included in the test protocols for the calculation of delamination toughness values are invalidated by the presence of the through-the- thickness reinforcement, they are used here as the best currently available means of normalising the fracture results However, these data reduction methods do not allow direct quantification of effects of the different pinning parameters on the crack bridging capability of the through-the- thickness reinforcement In order to relate the micromechanics at the pin level with the Mesomechanics of the delamination fracture specimens, the determination of the traction laws of a single Z-Fibre, bridging a crack and deformmg under various loading conditions, have been determined successfully by single pin experiments A finite element approach, utilising these experimentally determined single pin bridging laws, is presented as a tool to cany out parametric studies of the effects of pin length, diameter and location on the behaviour of delaminating beams The good agreement between the simulated and experimental R-curves demonstrates that the mode I delamination behaviour of DCB specimens is related to the single pin pullout traction laws Finally, preliminary studies of the compression after impact behaviour of ZFibreTh reinforced laminates indicate the existence of a complex relationship between the dramatic enhancement of the delamination crack propagation resistance of a material and the much lower (up to 50%) ultimate improvement in its compression after impact performance
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Jin, Siyu. "Monitoring the interface of carbon fibre and epoxy microcomposites using Raman spectroscopy with single walled carbon nanotubes as strain sensors." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/monitoring-the-interface-of-carbon-fibre-and-epoxy-microcomposites-using-raman-spectroscopy-with-single-walled-carbon-nanotubes-as-strain-sensors(4a371e26-386b-4512-8790-dcd928d90b43).html.
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The interfacial micromechanics of both high modulus and low modulus carbon fibres have been investigated using Raman spectroscopy. The innovative step was to make low modulus carbon fibres more Raman active by coating them with SWNTs to act as as a strain sensor. Two types of SWNTs have been employed; namely HiPCO SWNTs and COOH SWNTs. Single fibre deformation tests were carried out and the Raman band shift rates with respect to fibre strain have been determined. Meanwhile, different SWNTs coating methods have been investigated. The method of adding COOH SWNTs into the silane layer and within a hot cured epoxy layer was found to generate the highest band shift rates. Furthermore, an investigation of the effect of SWNTs on the strength of the interface was also carried out. A coating of COOH SWNTs was found to significantly improve the interfacial shear strength. Micromechanical tests have been carried out and the stress transfer between the carbon fibres and an epoxy resin was monitored using three different model composite geometries; namely microdroplet-fibre, a film-fibre and a standard fragmentation approach. The result of interfacial shear stress determined from microdroplet-fibre method varied and was found to be highly dependent on the droplet size and shape; this gave the lowest values of interfacial shear stress (ISS). The method of film-fibre obtained an intermediate ISS value which is between that from the microdroplet model test and the fragmentation test. The standard fragmentation test using Raman technique gives the highest ISS and HiPCO SWNTs were found to be a better strain sensor without affecting the original interfacial properties.
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Whittaker, A. J. "Thermal transport properties and microstructure of a series of carbon/carbon fibre composites." Thesis, University of Manchester, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375729.
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Williams, John David. "Plasma treatment of carbon nanotubes and carbon fibre for use in composite materials." Thesis, University of Bristol, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.629010.
Full textAbstract:
The performance of components, structures and vehicles are always in some way limited by the materials they are made from , often leading to compromises. This drives development to invent and discover new materials or processes to improve upon the current state of the art. In this respect the research contained in this thesis has investigated the use of plasma treatment~ as a method for modifying the properties of carbon nanotubes and carbon fibres to improve upon current composite materials technology. The initial study focused on functionalising relatively large quantities of carbon nanotubes using a unique and scalable technique suitable for industrialisation. The research began with a standard oxygen and ammonia treatment, which led to the development of an oxygen plasma treatment for increased carboxyl functionality. The important discoveries were that processing time and gas pressure had a large impact upon the agglomerate size, bulk density, surface energy, solvent stability and the quantity of carboxyl functionalisation. The treated carbon nanotube~ developed in the initial study were investigated for their use within an epoxy system. The treated carbon nanotubes were shown to disperse better, reduced resin viscosity, increase resistivity, but had little effect upon mechanical properties, degree of cure or glass transition temperature compared to the untreated carbon nanotubes. The development of the oxygen treated carbon nanotubes led the research to investigate if these treated carbon nanotubes could be used to improve the fracture toughness of a pre-preg system. The results showed that it was possible to improve initiation and propagation mode I fracture toughness significantly. Mode II results also showed increased initiation but relatively unchanged propagation toughness at lower areal densities, however in both mode I and II at the highest carbon nanotube coating density the fracture propagation resistance was reduced. The final study looked into the use of plasma treating carbon fibres as a method to modify the fibre matrix interface. The interface strength was found to improve for short oxygen and ammonia treatments, while reduce for the tetrafiuoromethane treatment on the unsized fibres . However for the commercially sized fibres each plasma treatment appeared to damage the propriety treatment in terms of interface strength. A further investigation into attaching carbon nanotubes to carbon fibres showed a dramatically reduced interface strength. The research demonstrates a variety of methods which could be used to tailor the interface for improved strength or damage tolerance.
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Marston, C. "An investigation of the strength and interface properties of single carbon fibres and carbon fibre tows in an epoxy resin." Thesis, London South Bank University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.618647.
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Das, Chakladar Nilanjan. "Multi-scale modelling of fibre assemblies." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/multiscale-modelling-of-fibre-assemblies(3edcc8fd-0c26-47bf-b427-9b54c944734c).html.
Full textAbstract:
Manufacturing of textile preforms involve preform compaction which influences the fibre volume fraction and level of crimp in the final laminates affecting the laminate properties. The preform compaction behaviour is highly non-linear and depends on a number of tow-level factors which in turn is guided by filament-level interactions. Hence experimentally predicting the compaction behaviour of a preform, made of large fibre bundles, remains as an obstacle to the understanding of the compaction mechanics due to the stochastic effects of filament-level interactions. This thesis proposes a novel multi-scale modelling technique which predicts the compaction behaviour of large fibre bundles or tows. The model considers real inter-fibre frictional interactions; the friction coefficients are obtained by carrying out friction tests on carbon fibres. Since the inter-fibre friction varies with the inter-fibre orientation, experiments are done to study the effects of fibre orientation on friction. The tests have shown a significant increase in coefficient of friction (from 0.2 to 0.45) for parallel tows due to bedding and entanglement of fibres in comparison to the friction between perpendicular tows. Modelling of the filament-level compaction behaviour requires inter filament friction coefficient which is not equal to the tow friction. In addition, the filaments within a tow can slip relative to each other. Therefore, inter filament friction can influence tow friction. Hence filament friction is determined from tow friction and used in the compaction models. Numerical models of compaction of large fibre bundles are developed which use this experimentally-obtained fibre friction coefficient as input. The solid model requires extensive computational effort. A two-dimensional (2D) model has been developed where the bending and torsional behaviour are incorporated with the help of springs. This 2D model has resulted in improved computational efficiency compared to the solid model (that is, a 99% improvement in CPU time for a 37 filament assembly). The model is then extended to tow- and fabric-levels. The tow-scale results are in close agreement (~5%) with validation tests. A further 3D modelling technique using beam elements has been presented as a further scope which is able to use the level of compaction obtained from the 2D model and also overcomes the limitations of the 2D model. This 3D modelling technique has shown 88% reduction in CPU time compared to that of solid model of same fibre bundle.
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Creighton, C. "The role of fibre alignment in the axial compressive failure of carbon-fibre polymer composites." Thesis, University of Cambridge, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.598144.
Full textAbstract:
The axial compressive strength of long-carbon fibre reinforced polymer matrix composites is known to be much lower (60% or less) than the tensile strength. The poor compressive strength is strongly associated with fibre misalignments which inevitably occur during the manufacturing process. Therefore, it is essential to be able to quantify the fibre alignment distribution in these materials. In the light of the fact that existing methods of alignment characterisation are very small scale procedures, extracting data from relatively few fibres, a new technique is presented with which information can be obtained on a much larger scale, yet within a reasonable time. A programme of experiments has been completed in order to determine the compressive strength of carbon-fibre reinforced polymer composites. Materials with varying degrees of fibre alignment and porosity have been investigated. The design of a new compression rig was required, the validation of which was accomplished using experimental results and numerical methods. The work described in this thesis addresses the observed failure mechanisms in well-aligned pultruded material and laminated composites with a wider distribution of fibre misalignments. It has been shown that, where measured fibre misalignments are very small, failure is due to fibre kinking, a localised instability (associated with the shear yielding of the matrix on planes parallel to locally misaligned fibres) as opposed to fibre crushing - governed by the intrinsic strength of the fibres themselves. The difficulty of testing representative volumes of material has been discussed but, when done so, it has been shown that elongated pores (approximately 2-3 fibre diameters in width) strongly influence the compressive strength. Numerical modelling has shown that local stress concentrations about such pores might be expected to act as sites for preferential nucleation of kinkbands.