Dissertations / Theses: 'Fibre composite'

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Farooq, Mohammed. "Development of FRP based composite fibre for fibre reinforced cementitious composites." Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/57668.

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This thesis describes a method of development of a novel fibre based on fibre reinforced polymers (FRP), for use fibre reinforcement in concrete. Thermosetting epoxy resin matrix were reinforced with E-glass, S-glass, and Carbon fibre to produce different types of composite fibres. The FRP panels were produced using the Vacuum Infusion technique, and then cut to different fibre sizes. The volume fractions of reinforcements within the FRP fibre were controlled by using woven and unidirectional fabrics. The number of layers of reinforcing fibres were also changed, to obtain the optimal thickness of the fibres. The FRP material was characterized by means of tensile tests and microscope image analysis. Four different compositions of FRP were produced with tensile strengths ranging from 195 MPa to 950 MPa. The different combinations in geometry broadened the total number of fibres investigated to 12. Single fibre pullout tests were performed to obtain the fundamental fibre-matrix interfacial bond parameters for the different FRP fibres. The FRP fibres, being hydrophilic, along with having a unique rough surface texture, showed a good bond with cement matrix. A bond strength superior to industrially available straight steel fibres and crimped polypropylene fibres has been observed. The 3 best fibres were then chosen to examine the flexural behaviour FRP fibre reinforced concrete beams. The optimized FRP fibres, one each of Glass FRP and Carbon FRP were then further investigated to study the effect of matrix maturity, temperature, fibre inclination, and loading rate on the fibre-matrix interfacial behaviour using single fibre pullout tests. Scanning Electron Microscope (SEM) analysis was carried out to identify the effect of above-mentioned factors on the surface characteristics of the fibre. An attempt was also made to optimize the fibre-matrix interface to achieve an optimized failure mechanism by coating the fibre with oil. The ability of the fibre to transfer stresses across a cracked section over extended periods has been investigated by means of fibre-relaxation tests. Finally, to assess durability, the fibres were conditioned at high pH and high temperature after which single fibre pullout, direct tension tests, & SEM analysis were conducted. Applied Science, Faculty of Civil Engineering, Department of Graduate

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Thanomsilp, Chuleeporn. "Toughening composites for liquid composite moulding." Thesis, Queen Mary, University of London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390838.

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Wood, Geoffrey Michael. "Treatment of polyethylene fibre for improved fibre to resin adhesion in composite applications." Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/28528.

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Tensile properties of polyethylene fibres are shown to be very good in comparison to properties of other advanced composite reinforcing fibres. Nevertheless, the use of polyethylene fibres in polymeric matrix composites suffers due to a poor fibre to resin adhesion. However, its ballistic properties are excellent because of the poor adhesion and also fibre ductility. Applications involving structural use of polyethylene fibres are limited by, among others, the low compressive and shear strengths. These are affected strongly by the degree of adhesion. Improvements in bonding are expected to result in greater commercial appeal for the fibres as the property limitations are reduced. Ultra Violet radiation has been shown previously, in laboratory scale batch studies, to induce graft co-polymerization of monomers to polyethylene films. Improvements in wettability and adhesion result when the grafted polymer is compatible to the bonding medium. In this study the technique was adapted to bench scale, continuous fibre treatment, whereby the monomer was surface grafted to the polyethylene substrate. Acrylic acid monomer was used for this due to its relative safety, small molecular size, and high reactivity. Reaction initiation was provided by use of a benzophenone photosensitizer due to the stability of polyethylene to UV radiation. The reaction was performed by pre-coating the fibres with reactants, then exposure to UV radiation. Results of the continuous process for fibre treatment indicate that the monomer concentration and temperature of the preliminary soakings are key variables. Adhesion improvement was measured by single fibre pullout tests and interlaminar shear strength (ILSS) tests. Of these, the ILSS appeared to be more sensitive for judging small improvements. Tensile tests were used to judge property deterioration due to treatment, and flexural property tests gave a preliminary indication of material behavior. The ILSS showed marked improvement from 1.5 ksi for untreated material to over 5.2 ksi for the better treatments. A competing treatment, plasma, shows ILSS values around 3 ksi. The flexural test indicated that failure of UV-grafted polyethylene was in tension, whereas failure of plasma and untreated material was in compression. The study has proven successful in improving the adhesion of polyethylene fibres to an epoxy resin matrix. Commercial viability is currently being developed through decreased process residence times and irradiation exposures. Applied Science, Faculty of Materials Engineering, Department of Graduate

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Goh, Kheng Lim. "Fibre reinforcement in fibre composite materials : effect of fibre shape." Thesis, University of Aberdeen, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.395069.

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The aim of this project was to investigate the effects of fibre shape on its ability to reinforce a fibre composite material. Analytical and finite element (FE) models of an axisymmetric fibre composite material were developed and used to achieve this aim. Fibres of cylindrical shape, ellipsoidal shape, with paraboloidal ends and with conical ends were considered: fibre geometry was further characterised by an axial ratio, q. The scope of this study covered elastic and plastic load transfer processes. The former corresponds to the initial loading stage whereby an applied tensile stress acting on a fibre composite causes stress in an elastic matrix to be transferred to an elastic fibre which is embedded in and adheres to the matrix. The latter corresponds to the next stage when, on progressive increase of the applied stress, the matrix yields and turns plastic and failure of adhesion at the fibre-matrix interface occurs. Two approaches were used to develop analytical models. In the first approach, equations were derived for calculating stress and displacement distributions in a general axisymmetric body. This approach was based on a stress function method for structural analysis of a statically indeterminate problem. The equations derived were implemented to model a fibre composite undergoing elastic load transfer by prescribing appropriate boundary conditions. However, the approach led to no useful solutions. In the second approach, first-order ordinary differential equations for solving axial, σz, and surface radial, σr, stresses in a fibre were formulated by considering forces at equilibrium in a stress element in a fibre subjected to a fibre-matrix interfacial stress. Equations for calculating these stresses to study plastic load transfer were derived from the differential equations by prescribing appropriate boundary conditions, σz was assumed to be constant in the radical direction of the fibre. For a cylindrical fibre, σz increases linearly, from zero at the ends, to a maximum value at the centre. At the other extreme, σz in a conical fibre was shown to be constant. The intermediate cases of a paraboloidal and an ellipsoidal fibre showed distribution of σz lying between these two extremes. The effectiveness of a fibre shape for reinforcement was defined for the plastic study. It was found that the conical fibre possessed the highest value; the cylindrical fibre gave the lowest value. From this study, it was concluded that: (1) an important property of all the tapers considered is to make the distribution of σz in a fibre more uniform; (2) fibres with conical ends are more effective for reinforcing fibre composite materials than cylindrical fibres.

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Lee, Ching Hao. "Fire retardant behavior of Kenaf fibre reinforced Floreon composite." Thesis, University of Sheffield, 2018. http://etheses.whiterose.ac.uk/19908/.

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According to the report, more than 41% of fatalities in flight were to find to be caused by fire. In recent years, composites used in aircrafts are carbon fibre/ glass fibre reinforced epoxy, due to light weights and high strength properties. However, these composites are known as highly flammable. Serious fire incident will be created in a short time after a spark of fire. Furthermore, ingredients for fibre and epoxies are, toxic and resulting in the release of toxic gases during fire, and cutting off fresh air to survivors and hindering their escape. In the meantime, biopolymers have attracted considerable attention due to their environmentally friendly and sustainable nature, Kenaf Fibre (KF) is one of the most famous natural fibre used as a reinforcement in Polymer Matrix Composites (PMC). Kenaf is also known as Hibiscus Cannabimus L., and is an herbaceous annual plant that is grown in a wide range of weather conditions, growing more than 3 meters within 3 months. However, the inherent drawbacks associated with Floreon (FLO) based composites include brittleness, lower strength and high moisture sensitivity, which in turn limit their application in the aircraft industry. In order to overcome such drawbacks, two modification techniques were employed in this study: (1) incorporated kenaf fibre into polypropylene polymer with magnesium hydroxide flame retardant and (2) reinforces kenaf fibre and magnesium hydroxide by different combination of volume. Consequently, KF reinforced FLO or polypropylene (PP) composites with magnesium hydroxide (MH) flame retardant specimens were successfully developed using extrusion followed by hot pressing. The increment of KF contents in PP composites had shown higher tensile modulus and decomposed mass loss at onset temperature, but lower values in tensile strength, elongation, flexural strength and onset temperature. In the meantime, 25 wt% KF contented PP composite shown a slightly higher flexural strength, while the higher volume of MH filler in composites caused lower strength, tensile modulus, elongation, but with higher onset temperature and the 2nd peak temperature in thermogravimetric analysis (TGA) testing. Furthermore, increasing the KF contents in PP matrix has found lower mass residue. However, increasing of KF contents in MH contented composite had increased the mass residue at the end of the testing. On the other hand, the increment of the melt flow properties (MVR and MFR) was found for the KF or MH insertion, due to the hydrolytic degradation of the polylactic acid (PLA) in FLO. The deterioration of the entanglement density at high temperature, shear thinning and wall slip velocity were the possible causes for the higher melt flow properties. In the meantime, increasing the KF loadings caused the higher melt flow properties while the FLO composites with higher MH contents created stronger bonding for higher macromolecular chain flow resistance, hence, recorded lower melt flow properties. However, the complicated melt flow behavior of the KF reinforced FLO/MH biocomposites was found in this study. The high probability of KF-KF and KF-MH collisions was expected and there were more collisions for higher fibre and filler loading, causing lower melt flow properties. Besides that, insufficient resin for fibre wetting, hydrolytic degradation on the biopolymer and poor interfacial bonding were attributed to low strength profile. Yet, further addition of KF increased the tensile strength and flexural. Nevertheless, inserting KF and MH filler have shown positive outcome on flexural modulus. Insertion of KF and MH showed the deterioration of impact strength, while the addition of KF increased the impact strength. Meanwhile, FLO is a hydrophobic biopolymer which showed only a little of total water absorption. In this regard, for the first 24 hours, the water absorption rates were high for all bio-composites. Hence, it is worth mentioning that the high contents of KF in bio-composites shown higher saturation period and higher total amount of water absorption while MH caused shorter saturation period but lower total amount of water absorption. However, interface bonding incompatibility has increased the water absorption of KF/FLO/MH composites. Moreover, some synergistic effect was located in char formation, Tg reduction and a lower tan δ peak shown in the three-phase system (KF/FLO/MH). The MH filler was found to be more significant in enhancing mass residual. The Tg were show deterioration for all samples compared to pure FLO biopolymer. The melting temperature has found no meaningful change for either insertion of KF or MH or both. The values of co-coefficient, C recorded decreasing as increasing the fibre loading. This showing the fibres transfer the loading effectively. As conclusion, although 10KF5MH specimen does not have the best performance in mechanical properties, a higher flame retardancy shall provide KF reinforced FLO composite with MH filler for more applications in advanced sector especially, in hazardous environment.

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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/époxy Carbon 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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Shuaib, Norshah. "Energy efficient fibre reinforced composite recycling." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/energy-efficient-fibre-reinforced-composite-recycling(554f1670-c818-4c74-9bfc-af3b51317e9b).html.

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Composite materials are widely used in various sectors such as aerospace, automotive and wind energy. Global increase of demand, particularly for fibre reinforced plastic (FRP) composites, unavoidably lead to high volumes of manufacturing and end of life waste. Currently, the most common disposal route for composite waste is through landfill. However, current and impending legislations such as Directive on Landfill of Waste (1999/31/EC) and End of Life Vehicle (ELV) Directive (2000/53/EC), have limited the amount of composite waste permitted for landfilling. In addition, production of virgin composite materials requires higher energy input in comparison to other counterpart materials such as steel and aluminium. This calls for an urgent need for composite waste to be recycled and reused in close loop and cross sector applications. The composite materials have a heterogeneous nature. Thermoset matrixes, which are used in most high grade applications, have three dimensional cross-linked structures which make melting and remoulding impossible. Such complex nature requires appropriate composite recycling technologies, a number of which are currently under research and development. At this early stage it is important to select and develop sustainable solutions in terms of economic performance and reduced environmental impact. Unfortunately at present, there is limited high integrity environmental related data in literature to help assess the life cycle benefits of composite recycling. This information is vital in exploring environmental credentials of composite recycling processes, and to ensure resource efficient use of manufacturing and end of life composite waste. The work reported in this PhD thesis deals with the investigation of energy demand of composite recycling processes. Composite waste and demand in the UK market was captured through Sankey diagrams. The diagrams, combined with environmental footprints of virgin material and recycling processes, were used to identify resource benefits of composite recycling initiatives. Furthermore, environmental data for mechanical recycling of glass fibre composites was derived through new and novel bottom up process science inspired mathematical energy modelling approaches. It was found that the process specific energy demand is dependent on the processing rate. The effects of key process variables in mechanical recycling on process energy demand and recyclate quality were also investigated. This study highlights the importance of selecting the right conditions for running recycling processes and generating recyclate with a high market value. Potential of new recycling techniques, namely high voltage fragmentation, was also assessed. Performance of the method, which was originally developed for fracturing rocks, was compared to the mature mechanical recycling process. The final part of this study used a life cycle assessment method to evaluate end of life options for an automotive composite product with the highlights on positive environmental impacts of recycling scenarios. Collectively, the findings from this study have brought together considerations on environmental and maturity status of composite recycling processes, into a comprehensive and updated analysis. The vision is that the knowledge integration between environmental and performance aspects will promote the concept of sustainable use of composite materials and a circular economy. The new datasets developed will enable end of life options for composite waste to be evaluated in life cycle assessment. In the absence of such information, the life cycle impact of composite material use in products cannot be fully or correctly evaluated.

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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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Fox, David Christopher Alexander. "The fire performance of restrained polymer-fibre-reinforced concrete composite slabs." Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/17998.

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Composite slab flooring systems for steel-framed buildings consist of a profiled steel deck and a cast in-situ slab. The slab traditionally includes a layer of light gauge steel mesh reinforcement. This mesh is placed near the surface, which controls the early-age cracking caused by concrete drying and shrinkage. The steel mesh also performs a vital structural role at high temperatures. Structural fire tests and numerical investigations over the last 15 years have established that the mesh can provide enhanced fire resistance. A load-carrying mechanism occurs in fire with the mesh acting as a tensile catenary, spanning between perimeter supports. This structural mechanism is currently utilised regularly in the performance-based fire engineering design of steel-framed buildings. In a recent development, this mesh can be removed by using concrete with dispersed polymer fibre reinforcement to form the composite slab. The polymer-fibre-reinforced concrete (PFRC) is poured onto the deck as normal, and the fibres resist early crack development. For developers this technique has several advantages over traditional reinforcing mesh, such as lower steel costs, easier site operations and faster construction. However, to date the fire resistance of such slabs has been demonstrated only to a limited extent. Single element furnace tests with permissible deflection criteria have formed the basis for the fire design of such slabs. But these have not captured the full fire response of a structurally restrained fibre-reinforced slab in a continuous frame. The polymer fibres dispersed throughout the slab have a melting point of 160ºC, and it is unclear how they contribute to overall fire resistance. In particular, there has been no explanation of how such slabs interact with the structural perimeter to maintain robustness at high deflections. This project was designed to investigate the structural fire behaviour of restrained polymer-fibre-reinforced composite slabs. An experimental series of six slab experiments was designed to investigate the effects of fibre reinforcement and boundary restraint. A testing rig capable of recording the actions generated by the heat-affected slab was developed and constructed. Model-scale slab specimens were tested with different reinforcement and perimeter support conditions, to establish the contributions to fire resistance of the polymer fibres and applied structural restraint.

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Leung, Ian Kin-Hay Electrical Engineering &amp Telecommunications Faculty of Engineering UNSW. "Development of composite cavity fibre lasers for fibre laser hydrophone systems." Publisher:University of New South Wales. Electrical Engineering & Telecommunications, 2008. http://handle.unsw.edu.au/1959.4/41248.

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In this thesis, my main focus was to establish a novel composite-cavity fibre laser (CCFL) and to apply it in sensing, particularly in the hydrophone application. The CCFL that I have proposed is formed by writing three wavelength matched fibre Bragg gratings directly into a continuous length of doped fibre. I have also examined the relative advantages and disadvantages of interferometric and intensity-based hydrophone systems, and have established a hydrophone system that can be switched between the two modes of operation, by making use of digital signal processing. I have established a theoretical model to study the lasing and spectral characteristics of the CCFL. My analysis showed that whilst the CCFL have significantly different phase and threshold conditions from the common semiconductor diode lasers with external cavity, the CCFL also have mode-limiting properties that are often sought after. Through simulations, I was able to identify that a non-uniform straining scheme, that is, when one of the sub-cavities of the CCFL is restrained from strain, can improve the sensitivity with respect to existing single cavity fibre lasers, in both the frequency and intensity domains. My simulations also showed that the sensitivity of such a straining scheme can be optimised by tuning the reflectivity of the gratings, sub-cavity lengths, doping concentration and pump power. I have fabricated multiple CCFLs using the in-house grating writing facilities, and have experimentally assessed their power and spectral related lasing characteristics. Whilst having a significantly longer total cavity length compared to typical fibre lasers, the CCFLs demonstrated stable single longitudinal mode operation and narrow linewidth in the order for a few tens of kHz. Asymmetric output power and frequency as a result of unequal sub-cavity lengths were also examined. Finally, I conducted sensing experiments by applying the CCFLs in strain monitoring and intensity-based hydrophone. My results showed that the non-uniform straining scheme had significantly improved the intensity response of the CCFL, and that the acoustic pressure and frequency can be determined by directly sampling and applying Fourier transform to the output intensity of the fibre laser.

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Gaffiot, Lauric. "Optimisation d’un procédé d’élaboration d’un composite à base de fibres naturelles." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAI056.

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Les matériaux composites constituent aujourd’hui un domaine très dynamique tant au niveau de l’industrie que de la recherche. Dans ce cadre, les renforts d’origines naturelles représentent une alternative intéressante aux fibres synthétiques de par leurs propriétés mécaniques élevées, leur faible densité et leur caractère biosourcé, afin de répondre à l’accroissement des niveaux de performances ciblés ainsi qu’aux exigences économiques et écologiques actuelles.Ces travaux s’inscrivent dans un projet regroupant laboratoires de recherche, fournisseurs et end-users, visant à développer un matériau composite unidirectionnel structural à base de fibre de lin pour une application sport et loisirs. Ainsi, les objectifs initiaux incluent le développement de différents traitements chimiques des fibres, afin de les laver, d’homogénéiser leurs propriétés mécaniques et d’améliorer l’adhésion fibre-matrice. Une stratégie originale a pour cela été élaborée, basée sur la réactivité et les propriétés physico-chimiques d’un agent de couplage biosourcé. Ce produit a montré un potentiel prometteur d’additif de renforcement des matériaux cellulosiques, notamment à l’état humide. De plus, sa réactivité avec des molécules compatibilisantes a permis de le fonctionnaliser pour promouvoir l’adhésion fibre-matrice.Les caractérisations menées aux différentes échelles de la fibre de lin ont ensuite montré la pertinence de ces traitements, qui renforcent les interfaces fibre-matrice et les fibres techniques à l’état humide. Les études mécaniques ont cependant soulevé de nombreuses problématiques expérimentales, et ont démontré que les spécificités morphologiques de ces objets et leur caractère naturel ne permettaient pas l’exploitation directe des mesures dans le cadre d’un tel projet de développement. Les axes de recherche se sont alors avant tout focalisés sur l’étude des matériaux composites. Ainsi, plusieurs verrous structuraux ont pu être identifiés. La qualité de l’imprégnation de ces renforts naturels, qui peut être influencée par la formulation des traitements et la mise en œuvre, est déterminante dans le développement du matériau à cause de la morphologie multi-échelles des fibres. L’orientation des fibres au sein des plis unidirectionnels s’est également avéré être un paramètre prépondérant, étroitement lié à l’architecture des renforts et aux procédés de traitements industriels.Les développements menés à la fois sur les traitements et sur la structure des composites ont ainsi permis de doubler les propriétés mécaniques des systèmes initiaux pour atteindre un module de rigidité de 30 GPa et une contrainte ultime d’environ 370 MPa en traction tout en limitant grandement la perte de résistance après vieillissement dans l’eau et en garantissant une déformation en flexion répondant au cahier des charges. Les évolutions réalisées ne permettent pas pour le moment d’envisager l’industrialisation de ce matériau, mais vont permettre le prototypage de produits finis Nowadays, composite materials are a challenging and dynamic thematic for both industry and academic research. In this context, natural fibres are an interesting alternative to synthetic fibres thanks to their high mechanical properties, low density and biosourced origins in order to meet the requirements in terms of performance, costs and durability.This work take part into an industrial project that include research laboratories, suppliers and end-users. It aims at developing a unidirectional flax fibre composite material for sport and recreation application. The initial objectives of development focused on the surface optimization and the reinforcement, and the improvement of fibre-matrix adhesion. An original strategy has been set, based on the reactivity and the physico-chemical properties of métapériodate oxidized xyloglucan. This molecule has shown a promising effect of reinforcement on cellulosic materials, particularly in wet conditions. Besides, its reactivity with compatibilization agents allows different functionalization possibilities to increase fibre-matrix adhesion, encouraging its use as a coupling agent.The characterizations led on the different scales of flax fibre validated this strategy, as micro-mechanical tests showed adhesion improvement and mechanical properties of wet fibres had significantly increased. However, further mechanical investigations rose numerous experimental issues, and demonstrated that the specific morphology of these objects as well as their natural origins were major obstacles to measures exploitation in this kind of development project. So, the main research axis then focused on directly composite materials.Different structural problematics has been thus identified. Natural fibre impregnation, which can be influenced by treatments composition and elaboration process, has revealed itself has an important parameter linked to the multi-scale organization of flax. The fibre orientation in the unidirectional ply has been also identified as a key parameter that is affected by reinforcement architecture and industrial process of treatment.Those developments on treatments and composite structure led to a great increase of the material tensile properties to reach 30 GPa modulus and 370 MPa in strength, also improving its water ageing behaviour and its flexion ultimate strain. These promising enhancements are not sufficient in terms of overall mechanical performance and elaboration process to envisage an industrialization phase, but the prototyping of finished products will be realized

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Le, Guen Marie Joo. "Damping behaviour of plant-fibre composite materials." Thesis, University of Canterbury. Mechanical Engineering, 2014. http://hdl.handle.net/10092/9978.

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The vibration damping property of plant fibres composites is of practical interest for commercial applications of biobased and eco-composites. Damping behaviour has been observed by experimentation and exploited in the marketing of sporting equipment but the origins of this behaviour have so far been only based on conjectures. In this thesis, the damping capacity of plant fibre composites was attributed to their chemical composition and the reversible interactions enabled by the breaking and reforming of hydrogen bonds under stress. The approach to explaining the mechanisms started with the characterisation of different plant fibre types to search for correlations between their physical and chemical structure. The investigation continued with quantifying the effect of hydrogen bonding compounds such as water, glycerol and polyglycerol on the damping coefficient of fibres and reinforced composites. The results of the polyol impregnation indicated that applying a pretreatment enhanced the vibration damping performance of flax reinforced composites, validating the hypothesis of the essential role played by hydrogen bonds in the fibres. The improvement in the damping coefficient of the composites was shown to be to the detriment of their stiffness. The compromised between the two properties was investigated in the final part of this thesis by using hybrid flax-carbon fibre reinforced composites.

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13

Hasanain, Fatin. "An experimental fibre-reinforced dental resin composite." Thesis, University of Newcastle upon Tyne, 2012. http://hdl.handle.net/10443/2023.

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Fibre-reinforced dental resin composites (FRCs) have shown increased fracture resistance and tensile strength compared with particulate filled composites (PFC). However, clinically successful restorative materials require adequate bond strength and wear resistance along with high strength. An experimental FRC (ST) was developed and tested as a dentine replacement. It has randomly distributed E-glass fibres above their critical length of 0.5-1.6 mm. This work aimed to evaluate the possibility of using ST as a single restorative material by assessing its three-body wear resistance and surface contact fatigue. The polymerisation shrinkage, water sorption, and bond strength of ST were also assessed. Two commercially available materials; an FRC (Build It FR) and PFC (Z250) were used as comparators. ST showed significantly lower wear resistance and higher contact fatigue. No significant difference was found regarding polymerisation shrinkage but ST had significantly higher water sorption, lower shear bond strength (SBS) to human dentine. SBS of the interfacial layers within and between the dental resin composites was evaluated after 24 hours and 1 year of water storage in the absence of an oxygen inhibition layer. Build It/Z250 showed a significantly higher SBS at both time intervals. The presence of an oxygen inhibited layer increased the interfacial strength in all groups except ST/Z250. ST formulations were varied in resin/diluent (Bis-GMA/TEGDMA) ratios, filler loading and fibre lengths for development. Wear testing found changing the Bis-GMA/TEGDMA ratio from 60/40 to 70/30 decreased the wear resistance regardless of filler loading and fibre length. In summary, wear resistance of ST and its variants was insufficient to recommend its use as a single restorative material without a surface veneer of PFC. As a dentine replacement, ST was only comparable with Z250 and Build It in polymerisation shrinkage and SBS between composites in the absence of an oxygen inhibition layer.

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Deshmukh, Sandeep Prabhakar. "Composite hollow fibre membranes for gas separation." Thesis, University of Leeds, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.423301.

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Al-Obad, Zoalfokkar. "Designing PU resins for fibre composite applications." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/designing-pu-resins-for-fibre-composite-applications(561553ad-7bf1-4507-891a-00743c776637).html.

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This thesis focuses on designing thermoplastic composites with high mechanical properties and a low processing temperature. Thermoplastic composites, which are used in this work, are composed of thermoplastic polyurethane (TPU) matrices and plain woven E-glass fabrics (GFs). TPUs were synthesised with large quantities of hard segments (HS), including 70% and 90%wt HS. The GF-TPU composites manufactured in this study have a melting point of around 175oC. As such, 180oC represents the processing temperature, which was used to produce GF-TPU composites. The influences of HS content and annealing treatment at 80oC on the thermal, dynamic mechanical and mechanical properties of TPU samples and GF-TPU composites with 25% fibre volume fraction (Vf) have been investigated. The highest crystallinity, storage modulus, Tg, yield strength, tensile strength and tensile modulus of all the TPU samples are seen in the TPU/90 samples annealed for 4 days. The TPU/90 samples display higher tensile properties than the TPU/70 and polypropylene (PP) samples, while the PP samples show the greatest elongation at break point. Furthermore, the tensile properties of the TPU/70 and TPU/90 samples are much higher than those of commercial TPUs. As such, annealed GF-TPU/90 composites with 25% Vf present the greatest dynamic mechanical, flexural, and tensile properties. GF-TPU/90 composites with 25% Vf show higher flexural strength than GF-PP composites or GF-polyamide 6 (PA6) composites with the same Vf. The effects of fibre surface treatments on the mechanical properties of GF and GF-TPU/70 composites with 25% Vf have also been studied in this investigation. GF treated with burn-off treatment is found to exhibit the lowest tensile properties. The interfacial adhesion between GF treated by NaOH for 0.5hrs and a TPU/70 matrix is greater than between GF treated by acetone for 5hrs and a TPU/70 matrix. Silanised GF presents greater tensile properties than desized GF. Thus, enhanced interfacial adhesion and tensile, flexural, ILSS and GIC properties are observed in the silanised GF-TPU/70 composites than in the desized GF-TPU/70 composites. GF-TPU/70 composites based on GFs treated by NaOH for 0.5hrs then sized with 0.15%wt. aminosilane display the greatest interfacial adhesion, flexural properties, ILSS and GIC, damage tolerance and impact-damage resistance. Conversely, the lowest interfacial adhesion, GIC, damage tolerance and impact-damage resistance are seen in the GF-PP composites based on 25% Vf as-received GF. There is a significant increase in the tensile and flexural properties of GF-TPU/90 composites with increasing the Vf from 25% to 50%. Moreover, the flexural strength of GF-TPU/90 composites with 50% Vf is not only higher than that of GF-EP composites or GF-vinyl ester composites with normalised 50% Vf, but is also much higher than that of GF-PP composites with 50% Vf. Despite this result, GF-TPU/90 composites with 50% Vf show the lowest fracture toughness, impact-damage resistance and damage tolerance, which are improved by adding 25% and 50%wt. of TPU/70 to the TPU/90 matrix. GF-TPU/90 composites based on a modified matrix have higher GIC, GIIC, impact-damage resistance and damage tolerance than GF-TPU/90 composites based on an unmodified matrix. The GIC, GIIC, impact-damage resistance and damage tolerance of GF-TPU/90 composites based on a modified matrix increase with increasing the percentage of TPU/70. Hence, the highest GIC, GIIC, impact-damage resistance and damage tolerance are seen in the GF-TPU/90 composites based on a modified matrix with 50%wt. of TPU/70.

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Tenace, Michael A. "Optimal design of fibre composite pressure vessels." Thesis, University of Ottawa (Canada), 1990. http://hdl.handle.net/10393/5819.

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Fibre composite pressure vessels are replacing conventional metallic vessels because of their higher efficiencies (stored energy/unit weight). In this study, multi-layered fibre composite pressure vessels have been designed using a Direct Search method to simultaneously determine the optimal design parameters of layer thickness and wind angle (based upon maximum vessel efficiency according to an interactive failure theory). It was shown that the ability of the fibre composite pressure vessel to resist the internal pressure without failure increased with increasing total wall thickness, up to a certain limit, after which little or no increase in failure pressure was possible. It was also shown that an improved design of a fibre composite pressure vessel can be accomplished by increasing the number of individual equal thickness layers in the vessel wall. Additional improvement in the design can be obtained by allowing the thickness of each individual layer to vary, especially for thicker vessels. Peak vessel efficiency generally occurred at the same wall thickness, implying the efficiency is mostly affected by the type of fibre/matrix combination selected. A slight improvement in efficiency was noticed by increasing the number of individual layers and allowing their thicknesses to vary. Finally, the manufacturing and testing aspects are described.

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Bale, Jefri Semuel. "The damage observation of composite using non destructive testing (NDT) method." Thesis, Paris 10, 2014. http://www.theses.fr/2015PA100067/document.

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L'objectif de ce travail de thèse est d'étudier le comportement de l'endommagement des matériaux composites sous chargement statique et fatigue par contrôle non destructif (C.N.D) thermographie et soutenu par émission acoustique et la tomographie (CT scan). Pour cela, ce unidirectionnels composite à fibres de verre (GFRP) et discontinue composite à fibres de carbone (DCFC) ont été utilisés comme les éprouvettes qui ont fourni par PSA peugeot citröen, France. Une série d'essais mécaniques a été réalisée pour déterminer le comportement de l'endommagement sous chargement statique et fatigue. Pendant tout des essais mécanique, la thermographie a été utilisé pour l'observation en temps réel pour suivre l'évolution des températures sur la surface de l'éprouvette et supporté par émission acoustique dans certaines conditions. Cette étude a utilisé une forme rectangulaire et se compose d'éprouvettes trouées et non trouées au centre de l'éprouvette. La vitesse de déplacement constante est appliquée pour observer l'effet sur le comportement de l'endommagement sous chargement de traction statique. Sous les essais de fatigue, le paramètre constant de la fréquence et de l'amplitude de stress a été étudiée pour chaque niveau de charge pour avoir les propriétés de fatigue et l'évolution de l'endommagement de l'éprouvette. La tomographie a été utilisée pour confirmer l'apparition de l'endommagement et l'etat du matériau après l'essai de fatigue. L'analyse des résultats de l'expérimentation et de l'observation NDT montré le bon accord entre les résultats mechnical et NDT thermographie avec prise en charge par l'observation de l'émission acoustique en détecter l'apparition et la propagation de l'endommagement de GFRP PRV et DCFC sous chargement de statique en traction. Les essais en fatigue montrent que la dissipation thermique est liée à l'évolution de l'endommagement et également thermographie et peut être utilisé avec succès pour déterminer la limite d'endurance (HCFS) et la courbe de Wöhler du matériau composite. Les résultats par CT scan ont mesurée avec succès les endommagements et l'état du matériau après essai de fatigue du matériau composite The aim of this study is to investigate the damage behaviour of composite material in static and fatigue condition with non destructive testing (NDT) thermography method and supported by acoustic emission and also computed tomography (CT) scan. Thermography and acoustic emission are used in real-time monitoring techniques during the test. On the other hand, NDT observation of tomography is used for a post-failure analysis. In order to achive this, continuous glass fiber composite (GFRP) and discontinuous carbon fiber composite (DCFC) have been used as the test specimens which supplied by PSA Company, France. A series of mechanical testing was carried out to determine the damage behaviour under static and fatigue loading. During all the mechanical testing, thermography was used in real-time observation to follow the temperature change on specimen surface and supported by acoustic emission in certain condition. This study used rectangular shape and consist of specimen with and without circular notches (hole) at the center. The constant displacement rate is applied to observe the effect on damage behaviour under tensile static loading. Under fatigue testing, the constant parameter of frequency and amplitude of stress was explored for each load level to have the fatigue properties and damage evolution of specimen. The tomography was used to confirm the appearance of damage and material condition after fatigue testing. The analysis from the experiment results and NDT observation shown the good agreement between mechnical results and NDT thermography with supported by acoustic emission observation in detect the appearance and propagation of damage for GFRP and DCFC under static loading. Fatigue testing shows that thermal dissipation is related to the damage evolution and also thermography and can be successfully used to determine high cycle fatigue strength (HCFS) and S-N curve of fiber composite material. From post failure analysis, CT scan analysis successfully measured and evaluated damage and material condition after fatigue test for fiber composite material. v

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Poutord, Antoine. "Étude du perçage à sec de l'empilage Ti6Al4V/Composite fibre de carbone." Thesis, Paris, ENSAM, 2014. http://www.theses.fr/2014ENAM0149/document.

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Le secteur aéronautique ayant des exigences toujours plus contraignantes, l’emploi de nouveaux matériaux pour les structures a été incontournable. C’est pourquoi le composite à fibre de carbone a fait son apparition dans les structures d’avions, épaulé par des pièces en alliage de titane, majoritairement du Ti6Al4V. Ces matériaux sont alors disposés en empilages et percés en une seule opération pour être ensuite assemblés par des rivets ou des boulons. Un certain nombre de problèmes, d’un point de vue industriel, sont soulevés par cette opération, générant des surcoûts importants. Les verrous technologiques et scientifiques liés à cette opération seront donc analysés au cours de cette étude.La connaissance des efforts locaux exercés par l’outil sur la matière usinée constitue un premier point permettant l’amélioration de la compréhension des phénomènes survenant lors de la coupe. Pour cela plusieurs procédés seront expérimentés pour déterminer avec précision les efforts subis par l’outil tout au long du perçage. Afin de compléter les informations relatives aux efforts sur l’outil, l’analyse de la température au sein du foret est nécessaire. Plusieurs dispositifs expérimentaux de mesure de la température in-situ sont développés.Ces dispositifs ont permis l’usinage instrumenté de trous à la fois dans chacun des deux matériaux composant l’empilage et dans l’empilage afin de comprendre au mieux les phénomènes survenant lors de ces opérations The aeronautic field has stronger and stronger requirements so the use of materials for structures has been unavoidable. That’s why carbon fiber composite is appeared in plane structures, used with elements in titanium alloy, and most part of them in Ti6Al4V. These materials are also dispatched in stacks and are drilled in a “one shot” operation, in the aim of being assembled with rivets or bolts. Through the industrial point of view, many problems are highlighted by this operation, generating several over costs. Technologic and scientific locks linked with this operation will be analyzed in this study.The knowledge of local stresses exerted by the tool on the machined matter is the first point allowing the improvement of the understanding of phenomenon that occurs during cutting. Few processes will be experimented to determine stresses submitted by the tool during drilling with accuracy. In the aim of completing the knowledge of the cutting operation, the analysis of the temperature inside the drill is needed. That’s why different experimental devices of thermal measurement are developed.These devices have allowed instrumented machining of holes in each material separately and in the stack of Ti6Al4V/CFRP in order to understanding phenomenon that occur during this operations

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Boillat, Pauline. "Energy efficient fibre composites recycling." Thesis, KTH, Materialvetenskap, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-298422.

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In this project, an investigation will be performed about how to improve thermal properties of recycled composite material. First, a literature study was performed about the potential techniques to improve the heating efficiency of the composites. Heating techniques, fibres and possible fillers were investigated. Secondely, an experimental method was set with the material available. In the laboratory a precedent work was performed on the thermal conductivity of polyamide 12 reinforced with glass fibres. The conductivity of polyamide 12 reinforced with carbon fibres is measured using the same experimental method to compare the thermal conductivity. In theory, carbon fibres have a better thermal conductivity than glass fibres, this was confirmed by the experiments performed. During the recycling of thermoplastic fibre composites the scrap will be grinded. Therefore, the thermal conductivity of small pieces of carbon fibre composites was measured, the thermal conductivity is reduced due to the increase of air fraction and the shortening of the fibres. The thermal conductivity of small pieces of glass fibre composite was investigated in the previous work, by mixing the grinded pieces of carbon fibre composite and the small pieces of the glass fibre composite the effect on the thermal conductivity was investigated. It was noticed that using smaller pieces of grinded material allows to reduce the air fraction between the bigger pieces and increase the thermal conductivity. I detta projekt kommer en undersökning att göras om hur man effektivt kan återvinna fiberförstärkta termoplaster. Först genomfördes en litteraturstudie om de potentiella teknikerna för att förbättra kompositernas uppvärmningseffektivitet. Uppvärmningstekniker, fibrer och möjliga fyllmedel undersöktes. Därefter genomfördes experiment med tillgängligt material. I laboratoriet hade tidigare ett arbete genomförts för att mäta värmeledningsförmågan hos polyamid 12 förstärkt med glasfibrer. Ledningsförmågan hos polyamid 12 förstärkt med kolfibrer kommer här att mätas med samma experimentella metod för att jämföra värmeledningsförmågan. I teorin har kolfibrer bättre värmeledningsförmåga än glasfibrer, detta bekräftades av de utförda experimenten. Under återvinning av kompositer av termoplastfibrer maldes restmaterialet ner. Därför mättes värmeledningsförmågan hos små bitar av kolfiberkompositer, värmeledningsförmågan minskades på grund av ökningen av luftfraktion och förkortningen av fibrerna. Värmeledningsförmågan hos små bitar av glasfiberkomposit undersöktes i det föregående arbetet, genom att blanda de slipade bitarna av kolfiberkomposit och de små bitarna av glasfiberkompositet undersöktes effekten på värmekonduktiviteten. Det noterades att användning av mindre bitar av slipat material gör det möjligt att minska luftfraktionen mellan de större bitarna och öka värmeledningsförmågan.

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Luke, David George. "Broadband optical fibre interferometry for strain measurement in composite materials." Thesis, Heriot-Watt University, 1997. http://hdl.handle.net/10399/655.

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Jia, Weiwei. "Polylactic acid fibre reinforced biodegradable composites." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/polylactic-acid-fibre-reinforced-biodegradable-composites(732904c8-584b-4fbb-b68a-3cf14dc84e9f).html.

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Polylactic acid (PLA) is a well-known biodegradable and sustainable polymer, derived from renewable agricultural sources. Its high price in the past limited its applications to mainly biomedical materials such as bone fixation devices. As the growth of awareness in global environment protection and sustainable development, PLA has attracted increased attention and development. Nowadays, the applications of PLA have been broadened into plastics, textiles and composites etc. Composites have been widely used in industrial applications for several decades, due to their high strength-to-weight ratio and good structural properties. However, most traditional composite materials are composed of two distinct fossil fuel based components. They are not eco-friendly and are difficult to recycle. This study aims at the development of PLA biodegradable composites and the optimisation of the processing parameters to achieve the best mechanical properties of PLA self-reinforced composites (PLA-SRC) for various end-uses. A variety of polymer analytical techniques were used to evaluate crystallinity, thermal properties, and chemical structures of the PLA reinforcement and matrix. Further study was carried out to assess the effects on mechanical properties of PLA-SRC caused by the processing temperature, pressure and holding time. The composites produced at high temperature and/or high pressure have significantly better matrix penetration (fibre wetting), which enhances mechanical properties. However, holding time was found to have no significant effect on the properties of PLA-SRC.

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Westin, Johan. "Ballistic Impact Properties of Fibre-Reinforced Composite Structures." Thesis, KTH, Farkost och flyg, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-39676.

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23

Beckermann, Gareth. "Performance of Hemp-Fibre Reinforced Polypropylene Composite Materials." The University of Waikato, 2007. http://hdl.handle.net/10289/2543.

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Increasing worldwide environmental awareness is encouraging scientific research into the development of cheaper, more environmentally friendly and more sustainable construction and packaging materials. Natural fibre reinforced thermoplastic composites are strong, stiff, lightweight and recyclable, and have the potential to meet this need. Industrial hemp fibre is amongst the strongest of the natural fibres available, and possesses a similar specific stiffness to E-glass, but with additional benefits such as low cost and low production energy requirements. The favourable mechanical properties of hemp, however, have yet to be transferred successfully to thermoplastic-matrix composite materials. The aim of this thesis was to achieve a greater understanding of the various parameters that contribute to composite strength and stiffness, and to manipulate these parameters in order to produce an improved hemp fibre reinforced polypropylene composite material. Hemp fibre was alkali treated at elevated temperatures in a small pressure vessel with either a solution of 10wt% NaOH or 5wt% NaOH / 2wt% Na2SO3. Single fibre tensile tests were performed on treated and untreated fibres, and it was found that the NaOH/Na2SO3 treatment produced the strongest and stiffest fibres with a good level of fibre separation. Lignin tests revealed that both alkali treatments were effective in the removal of lignin from hemp fibre, and XRD analysis showed that both alkali treatments resulted in increases in the hemp fibre crystallinity index. TGA and DTA analysis showed that the alkali fibre treatments improved the thermal stability of the treated hemp fibre when compared to the untreated fibre. Alkali treated hemp fibre, polypropylene and a maleic anhydride modified polypropylene (MAPP) coupling agent were compounded in a twin-screw extruder, and injection moulded into composite tensile test specimens. A range of composites with different fibre and MAPP contents were produced and tested. Tensile tests revealed that the optimum composite consisted of polypropylene with 40wt% NaOH/Na2SO3 treated hemp fibre and 4wt% MAPP, and had a tensile strength of 50.5 MPa and a Young's modulus of 5.31 GPa, respectively. The effect of MAPP on the fibre/matrix interface of NaOH/Na2SO3 treated hemp fibre/polypropylene composites was assessed by means of the single fibre fragmentation test. A composite consisting of NaOH/Na2SO3 treated fibres in a matrix of 4wt% MAPP and polypropylene was found to have a critical fibre length of 0.83mm and an interfacial shear strength of 16.1 MPa. The effects of MAPP on the composite fracture mechanisms were evaluated by means of SEM microscopy. TGA and DTA analysis showed that untreated hemp fibre composites and NaOH/Na2SO3 treated hemp fibre composites, each with a matrix of 4% MAPP and polypropylene, were less thermally stable than the polypropylene matrix alone. The Bowyer-Bader model was used to model the strength of an injection moulded composite with a normal fibre length distribution, consisting of 40wt% NaOH/Na2SO3 treated fibre, 4% MAPP and polypropylene. A theoretical composite tensile strength of 149 MPa was obtained from the model, based on the assumption that all the fibres were axially aligned in the composite. Composites with long, axially aligned fibres were produced using a novel solution mixing technique, where the polymer matrix and MAPP coupling agent were dissolved in a solvent and then precipitated inside an aligned fibre mat. Significant improvements in tensile strength and Young's modulus were achieved for solution mixed composites compared to composites produced by means of extrusion and injection moulding. The strongest solution mixed composite had a tensile strength of 84.7 MPa, and consisted of 56wt% NaOH/Na2SO3 treated fibre, 4% MAPP and polypropylene; and the stiffest injection moulded composite had a Young's modulus of 16.0 GPa, and consisted of 63wt% NaOH/Na2SO3 treated fibre, 4% MAPP and polypropylene.

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Thornton, David J. "Finite element analysis of fibre-reinforced composite pipeline." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0016/MQ47106.pdf.

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Carmai, Julaluk. "The modelling of matrix-coated fibre composite consolidation." Thesis, University of Oxford, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365724.

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Tridech, Charnwit. "Smart fibre coatings stiffness control in composite structures." Thesis, Imperial College London, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.529352.

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Bootkul, Duangkhae. "Fibre sensor for cure monitoring in composite materials." Thesis, University of Sheffield, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.440917.

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Jones, Simon Ellis. "Practical optimum internal fibre distribution in composite components." Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.627154.

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Ekström, Lars Johan. "Welding of bistable fibre-reinforced thermoplastic composite pipelines." Thesis, University of Cambridge, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.614933.

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Salama, Adel. "Laser machining of carbon fibre reinforced polymer composite." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/laser-machining-of-carbon-fibre-reinforced-polymer-composite(7310ed95-b876-480b-a8b4-2033b4309cb6).html.

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Carbon fibre reinforced polymer (CFRP) composites have found a wide range of applications in the aerospace, marine, sports and automotive industries owing to their lightweight and acceptable mechanical properties compared to the commonly used metallic materials. The currently dominating method of machining CFRP is by mechanical means that has found many problems including extensive tool wear, fibre pull-out and delamination. Lasers as non-contact tools have been widely applied for cutting and drilling materials. However, machining of CFRP composites using lasers can be challenging due to inhomogeneity in the material properties and structures, which can lead to thermal damage such as charring, heat affected zones (HAZs), resin recession and delamination. In previous studies, Nd:YAG, diode pumped solid state (DPSS), CO2 (continuous wave), disk and fibre lasers were used in machining CFRP composites and the control of damage such as the size of heat affected zones (HAZ) and achieving comparable material removal rate with the mechanical processes remain a challenge. Most reported work showed a typical heat affected zone of 0.2-1.2 mm. The availability of short pulsed transversely excited atmospheric (TEA) CO2 lasers and ultra-short laser pulse sources such as picosecond lasers make it possible to improve the laser machining quality of CFRP materials. In this research, the machining of CFRP composites using a microsecond pulsed TEA CO2 laser, a state of the art high power picosecond laser and a 1 kW single mode fibre laser system was investigated. The yielded heat affected zone was less than < 25 µm for the TEA CO2 and the picosecond laser machining, although the material removal rate was low. Additionally, it has been shown that the pulsed fibre laser improved the machining quality compared to that with the continuous mode. A potential application of the fibre laser for composite repair and remanufacturing was investigated. The interactions between picosecond laser beam and CFRP composite were studied in more detail including understanding the self-limiting effect in single and multiple parallel tracks drilling/machining through both experimental and theoretical studies. Furthermore, a sequential laser and mechanical drilling of CFRP was investigated to improve the machining rate. The work performed in this PhD was driven by aerospace industry needs, with the collaboration of Rolls-Royce plc and BAE Systems as industrial partners.

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Kim, Hyung Sun. "Development of a fibre-reinforced glass-ceramic composite." Thesis, Imperial College London, 1989. http://hdl.handle.net/10044/1/47512.

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Al-Haddad, Ala'A. "Characterisation and performance of fibre-reinforced composite restorations." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/characterisation-and-performance-of-fibrereinforced-composite-restorations(bdcc1685-a341-4b8a-9e4a-542467f4b321).html.

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In the modern era of metal-free minimally-invasive dentistry, there is a growing tendency toward using metal-free restorative alternatives that provide not only excellent aesthetics but also enable superior durability. Fibre-reinforced composite (FRC) is one cost-effective alternative that fulfils the requirements of aesthetics and durability, and offers favourable physico-mechanical properties. Many FRC applications are well-documented in the literature, such as crowns and fixed partial dentures (FPD); however, their clinical implementation is still limited, owing to the lack of significant knowledge about their longevity, deterioration signs, optimum design and overall performance. This in-vitro research aimed to address these uncertainties by investigating the performance of FRC restorations, and the influence of fibre reinforcement on particular physcio-mechanical properties, including surface hardness, edge-strength, shear bond strength, fatigue and wear resistance. Basic testing models were used to investigate the effect of incorporating differently-oriented FRCs on the surface hardness, edge-strength and shear bond strength of particulate-reinforced composite (PRC). The results revealed that the incorporation of FRC significantly enhanced surface hardness (by 12 - 19 %) and edge-strength (by 27 -75 %). However, this incorporation significantly reduced the shear bond strength (SBS) between PRC and other restorative materials, including lithium disilicate ceramic (10.9±3.1 MPa) and Co-Cr metal alloy (12.8±2.3 MPa), compared to the control (15.2±3.6 MPa, 15.0±3.7 MPa). The orientation of FRC was also found to affect the efficiency of reinforcement as bidirectional FRCs exhibited significantly higher hardness (76.8±1.2 VHN), edge-strength (67.7±8.2 N) and SBS (14.1±3.9 MPa) values than unidirectional FRCs (72.4±1.2 VHN, 56.8±5.9 N, 9.8±2.3 MPa).Clinically-relevant testing models, employing accelerated aging techniques, were performed to investigate the fatigue and wear behaviours of anatomically-shaped FRC restorations in-vitro. Direct inlay-retained FRC-FPDs with two framework designs, were tested for their fatigue behaviour and load-bearing capacity. Type-I design (with an additional bidirectional FRC layer incorporated perpendicular to the loading direction) yielded significantly higher fatigue resistance (1144.0±270.9 N) and load-bearing capacity (1598.6±361.8) than Type-II design (with a woven FRC embedded around the pontic core) (716.6±72.1 N, 1125.8±278.2 N, respectively). However, Type-19II design exhibited fewer delamination failures. Both framework design and dynamic fatigue were found to have a significant influence (p < 0.05) on the load-bearing capacity of FRC-FPDs. Additionally, the in-vitro fatigue and wear behaviours of FRC crowns, fabricated conventionally from bidirectional FRC and indirect PRC (Sinfony), were compared with those made of two CAD/CAM alternatives, namely Lava Zirconia (LZ) and Lava Ultimate (LU). A chewing simulator was employed to induce some fatigue wear in crowns, while an intraoral 3D scanner was used to quantify the resultant morphological changes. The results showed that FRC crowns had significantly lower mean cumulative wear (233.9±100.4 μm) than LU crowns (348.2±52.0 μm), but higher than LZ crowns (16.4±1.5 μm). The mean load bearing-capacity after fatigue simulation was also the highest for LZ crowns (1997.8±260.2 N) compared with FRC (1386.5±258.4 N) and LU crowns (756.5±290.9 N).Accordingly, the incorporation of FRC in resin-composite restorations is advocated since it increases surface hardness and marginal integrity, improves fatigue and wear behaviours, and enhances load-bearing capacity and overall performance.

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Arora, Hari. "Blast loading of fibre reinforced polymer composite structures." Thesis, Imperial College London, 2012. http://hdl.handle.net/10044/1/9625.

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The resistance of glass and carbon fibre reinforced polymer (GFRP and CFRP) sandwich panels and laminate tubes to blast in air and underwater environments have been studied. Explosive charges of 0.64-100 kg TNT equivalent were used during these studies. Procedures for monitoring the structural response of such materials during blast events have been devised. High-speed photography was employed during the air-blast loading of GFRP and CFRP sandwich panels, in conjunction with digital image correlation (DIC), to monitor the deformation of these structures under shock loading. Failure mechanisms have been revealed using DIC and confirmed in post-test sectioning. Strain gauges were used to monitor the structural response of similar sandwich materials and GFRP tubular laminates during underwater shocks. The effect of the supporting/backing medium (air or water) of the target facing the shock has been identified during these studies. Mechanisms of failure have been established such as core crushing, skin/core cracking, delamination and fibre breakage. Strain gauge data supported the mechanisms for such damage. A transition in behaviour was observed in the sandwich panels when subject to an underwater blast as opposed to an air-blast load. Damage mechanisms notably shifted from distributed core shear failure originating from regions of high shear in air blast to global core crushing in underwater blast. These studies were part of a research programme sponsored by the Office of Naval Research (ONR) investigating blast loading of composite naval structures. The full-scale experimental results presented in this thesis will aid and assist in the development of analytical and computational models. Furthermore, this work highlights the importance of support and boundary conditions with regards to blast resistant design. These outcomes were analysed further in finite element simulations of both air and underwater blast conditions, where boundary stiffness and support conditions were, as expected, shown to strongly influence structural response and deformation of the target.

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Vaziri, Reza. "On constitutive modelling of fibre-reinforced composite materials." Thesis, University of British Columbia, 1989. http://hdl.handle.net/2429/29311.

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A relatively simple but comprehensive constitutive model is presented herein for predicting the nonlinear behaviour of laminated composite structures comprising layers of unidirectional and/or bidirectional (e.g. woven) fibre-reinforced materials (FRMs). The FRM layer is treated as an orthotropic but homogeneous continuum undergoing isothermal infinitesimal deformation. The proposed constitutive model for single layers of FRM is built within the framework of rate-independent theory of orthotropic elastoplasticity. The constitutive equations so developed, are then superimposed using the classical lamination theory, to arrive at the governing response relations for multilayer laminates. The model invokes a 3-parameter quadratic yield surface and the associated flow rule of plasticity. During plastic flow the evolution of the yield surface in the stress space is described by a non-proportional change in the parameters of the initial yield function. A 3-parameter quadratic failure surface similar in form to that of the initial yield surface is defined to mark the upper limit of plastic flow. Once failure is reached, it is identified as fibre or matrix mode of failure depending on the relative magnitude of various stress ratio terms appearing in the failure criterion. In the post-failure modelling, both brittle and ductile type of behaviour are considered in the direction of the offending stress. Unidirectional and bidirectional FRM layers are treated within the same general framework with the exception that yielding (and failure) in these layers are assumed to be governed by different criteria, namely, Hill's and Puppo-Evensen's yield (and failure) criteria, respectively. To completely quantify the proposed elastic-plastic-failure model three pieces of experimental stress-strain curves are required, namely, the uniaxial stress-strain curves along the two principal axes of orthotropy, and the in-plane shear stress-strain curve. Once established, these stress-strain curves are represented by bilinear approximations thus clearly defining the key parameters under the various loading programs. No provisions are made for the difference between tensile and compressive responses. Based on the proposed model, constitutive equations are properly formulated. A nonlinear finite element code is developed to incorporate the derived constitutive equations. The program is based on the conventional displacement method finite element procedure using two dimensional 8-node isoparametric elements. The nonlinearities in the equilibrium equations are handled by a mixed incremental and Newton-Raphson iterative procedure. Analysis restart and cyclic loading capabilities are also included to expand the program's usefulness. The performance of the program and the effectiveness of the model are verified for a number of in-plane loading paths applied to a wide variety of laminated FRMs with and without geometric discontinuities. The favourable comparisons of the model to experimental results available in the literature support the validity of the model. Applied Science, Faculty of Civil Engineering, Department of Graduate

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Buck, Lyndon. "Furniture design with composite materials." Thesis, Bucks New University, 1997. http://bucks.collections.crest.ac.uk/9977/.

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This thesis examined the feasibility of fibre composite reinforcement in the furniture industry. The development of post war furniture design was reviewed, with particular emphasis on the main design movements and the use of new materials and technologies. The use of fibre composite materials in contemporary furniture was discussed in terms of technical development, environmental effects and psychological acceptance. Fibre reinforcements and adhesives were compared, as were fabrication techniques applicable to the existing British furniture industry. Particular emphasis has been placed on the fibre reinforcement of laminated timber sections as a method of overcoming many of the manufacturing problems of composites. Methods of analysing the behaviour under load of fibre reinforced laminated wood were reviewed. Resistance among the furniture buying public to modem, non-traditional furniture design was discussed, along with ways of making composite materials more aesthetically acceptable. Experimentation to determine the mechanical properties of fibre composite reinforced wood against wood control samples was undertaken, along with methods used to analyse the results for flat and curved samples. Modulus of elasticity, modulus of rupture and impact strength were measured, as was the level of distortion of the samples before and after testing. A full size chair form was produced to demonstrate the behaviour of the material on a larger scale. The development of the design was discussed in terms of ergonomic requirements, aesthetics, practicality and environmental concerns. The problem of predicting the behaviour of complex shapes was discussed and a finite element analysis of the form is carried out to gain an accurate picture of the composite's performance. Production of fibre reinforced materials was discussed, along with the furniture industry's reluctance to invest in new materials and technologies. The feasibility of adapting traditional furniture making skills and equipment to the production of fibre composite reinforced wood has been assessed.

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Zhuang, Linqi. "Les effets de la répartition non-uniforme des fibres sur la propagation des fissures á l’interface fibre/matrice dans les matériaux composites." Thesis, Université de Lorraine, 2017. http://www.theses.fr/2017LORR0321/document.

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Dans ces travaux, nous avons étudié numériquement la croissance du décollement de l'interface fibre / matrice d'un composite UD avec garnissage hexagonale de fibre sous charge longitudinal et transversal. Nous avons mis l'accent en particulier sur l'influence des fibres voisines sur sa croissance. Dans la présente étude, le taux de libération d'énergie (ERR) est considéré comme la force motrice de la croissance du décollement et a été calculé sur la base de Integral J et de la technique de fermeture virtuelle de fissures (VCCT) à l'aide du logiciel de calcul par éléments finis ANSYS. Dans la présente recherche de thèse, nous avons étudier d’abord l'influence des fibres voisines sur ERR d'une décohésion émanant d'une rupture de fibre en condition de chargement longitudinal. Dans le cas du chargement longitudinal, la croissance du décollement est gouvernée par le mode II. Comme point de départ l’étude, nous avons mis place un modèle axisymétrique composé de 5 cylindres concentriques représentant la fibre endommagée, la matrice environnante, les fibres voisines, la matrice environnante et le composite effectif généré. On constate qu'il y a deux stades de croissance, la première étape correspond à une longueur courte du décollement, l'ERR diminue à mesure que l'angle du décollement augmente, et la présence de voisins augmente significativement la décohésion de l'ERR. Pour une décohésion relativement longue, le décollement se situe dans une région de croissance en état stationnaire lorsque l'ERR est pratiquement constant quelle que soit la longueur du décollement. À l’état stationnaire de la croissance du défaut, la présence de fibres voisines n'a que peu d'effet sur l'ERR. Les travails ultérieurs, nous avons mis en place un modèle 3-D (explicite) avec la fibre endommagée et ses 6 fibres les plus proches dans un composite UD compacté hexagonal, entourées par le composite homogénéisé. Sur la base des résultats obtenus, nous avons montré que l'ERR varie le long de la face frontale et a son maximum à l'endroit circonférentiel où la distance entre deux centres de fibre est la plus petite. Cela indique que le front du décollement n’est pas circulaire. Pour l'état stable du décollement, la présence de fibres a peu d'effet sur l'ERR qui progresse le long du front du décollement. Pour un décollement court, la présence de fibres augmente l'ERRS moyenné, et cette augmentation est plus significative lorsque la distance entre fibre est la plus petite. Après l’étude du la décollement fibre / matrice en charge longitudinale, nous avons commencé à étudier la croissance du décollement fibre / matrice le long de la circonférence de la fibre sous charge transversale. On constate que la croissance de la du décollement est en mode mixte, et les composants ERR du mode I et du mode II augmentent avec l'augmentation de l'angle de déformation puis diminuent. La croissance du décollement démarre principalement en mode I pour les petits angles de décollement et se poursuit en mode II. La présence de fibres voisines a un effet d’accroissement sur la croissance du décollement jusqu'à certains petits angles et change ensuite en effet protecteur. En fin, nous avons étudié l'interaction entre deux décollement sous chargement transversale. Nous avons constaté que lorsque deux décollements sont proches l'un de l'autre, l'interaction entre devient beaucoup plus forte et conduit à l'augmentation significative de l'ERR de chaque décollement, ce qui facilite la croissance du décollement In the presence thesis, the growth of fiber/matrix interface debond of a UD composite with hexagonal fiber packing under longitudinal and transverse tensile loading was investigated numerically, with the special focus on the influence of neighboring fibers on its growth. In the current study, energy release rate (ERR) is considered as the driving force for debond growth and was calculated based on J Integral and Virtual Crack Closure Technique (VCCT) using finite element software ANSYS. In the present thesis research, we started with investigating the influence of neighboring fibers on ERR of a debond emanating from a fiber break in longitudinal loading condition. In longitudinal loading case, debond growth is mode II dominated. As the starting point for the research, an axisymmetric model consisting 5 concentric cylinders that represent broken fiber with debond, surrounding matrix, neighboring fibers, surrounding matrix and effective composites was generated. It’s found that there are two stages of debond growth, the first stage is when debond length is short, the ERR decreases with increasing debond angle, and the presence of neighboring significantly increase the ERR of debond. For relatively long debond, the debond is in a steady state growth region when ERR is almost constant regardless of debond length. In steady state of debond growth, the presence of neighboring fibers have little effect on the ERR. In the later research, a 3-D model was generated with broken fiber and its 6 nearest fibers in a hexagonal packed UD composite were modelled explicitly, surrounded by the homogenized composite. Based on the obtained results, it’s shown that ERR is varying along debond front, and has its maximum at the circumferential location where the distance between two fiber center is the smallest. This indicates the debond front is not a circle. For steady state debond, the presence of fibers have little effect on ERR that averages along debond front. For short debond, the presence of fibers increases the averaged ERRS, and that the increase is more significant when inter-fiber distance are the smallest. When we conclude our investigation on fiber/matrix debonding under longitudinal loading, we began studying the growth of a fiber/matrix debond along fiber circumference under transverse loading. It’s found that debond growth is mixed-mode, and both mode I and mode II ERR components increase with increasing debond angle and then decreases. Debond growth is mode I dominated for small debond angle and then switch to mode II dominated. The presence of neighboring fibers have an enhancement effect on debond growth up to certain small debond angle and then changes to a protective effect. Finally, the interaction between two arc-size debond under transverse loading is investigated. It’s found that when two debonds are close to each other, the interaction between two debond becomes much stronger, and that interaction leads to the increase of ERR of each debond significantly, which facilitates further debond growth for both debond

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Neagu, Razvan Cristian. "Hygroelastic behaviour of wood-fibre based materials on the composite, fibre and ultrastructural level." Doctoral thesis, KTH, Hållfasthetslära (Avd.), 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4098.

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Wood fibres can be used as reinforcement in plastics for load carrying purposes. Some advantages compared with conventional man-made fibres are that wood fibres come from a renewable resource, have high specific stiffness and strength, are generally less hazardous to health, biodegradable, and can be manufactured at low cost and high volumes. A clear disadvantage with cellulose-based materials for structural use is their dimensional instability in humid environments. The hygroelastic properties are of high importance in materials development of improved wood-fibre composites. This work deals with the stiffness and hygroexpansion of wood fibres for composite materials. The long-term aim is to design engineered wood fibre composites based on better basic knowledge of wood fibres. Mechanistic models have been used to link the fibrous microstructure with macroscopic composite engineering properties. The properties have been characterized experimentally for various wood-fibre composites and their fibre-mat preforms, by means of curvature measurements at various levels of relative humidity, as well as tensile and compressive tests. From these test results and microstructural characterization, the longitudinal Young’s modulus and transverse coefficient of hygroexpansion of wood fibres were identified by inverse modelling. Some effects of various pulp processes and fibre modifications on the elastic properties of the fibre were observed, illustrating how the mixed experimental-modelling approaches can be used in more efficient materials screening and selection. An improved micromechanical analysis for wood-fibre composites has been presented. The model is more appropriate to combine with laminate analogy, to link fibre properties on the microscale to the macroscopic composite properties and vice versa. It also offers the possibility to include the effects of ultrastructure since it can account for an arbitrary number of phases. An approach to model ultrastructure-fibre property relations has been demonstrated. It includes analytical modelling of multilayered cylindrical fibres as well as finite element modelling of fibres with irregular geometry characterized with microscopy. Both approaches are useful and could be combined with experiments to reveal insights that can pave way for a firmer link between the wood fibre ultrastructure and wood fibre properties. QC 20100914

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Neagu, Răzvan Cristian. "Hygroelastic behaviour of wood-fibre based materials on the composite, fibre and ultrastructural level /." Stockholm, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4098.

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Mulligan, D. R. "The effect of fibre-bundling on the mechanical properties of a short-fibre composite." Thesis, University of Surrey, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313260.

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It has been suggested that the use of fibre bundles rather than individual fibres can improve the toughness properties of a short-fibre composite. Previous experimental work on this topic employed materials in which bundles were impregnated prior to manufacture or materials with poorly defined fibre-bundling. This study is the first to consider the mechanical properties of a series of materials where the bundles have been impregnated during manufacture of the material, and the materials tested contained a well-defined proportion of fibres within bundles of a known size. A novel manufacturing technique has been developed that can be used to produce short carbon fibre reinforced polypropylene materials with a controlled proportion of fibres in bundles. Materials manufactured in this work contained 0 %, 25 %, 50 %, 75 % and 100 % of the fibres in bundles. The fibres had a length of 5 mm or 10 mm and the bundles contained either 1000 or 6000 fibres. An increase in the proportion of fibres within bundles results in a decrease in the tensile modulus of the short-fibre composites. This decrease was less severe for materials containing bundles with a greater aspect ratio or laminates with a greater thickness. A model for the modulus of the materials has been developed which illustrates some of the effects of fibre-bundling on the structure of a short-fibre composite. For the materials studied, tensile strength of materials containing bundles was one quarter of the tensile strength of the filamentised material. Only one combination of fibre length and bundle size resulted in a clear increase in toughness, as measured by JJ, compared to the filamentised material and this increase appears to be due to areas of unreinforced matrix in the material. Materials containing both filamentised fibres and fibre bundles had relatively low values of J, The fracture surfaces were imaged and three distinct ways in which a bundle may fail have been identified. Discussion of the fracture mechanisms active in these materials concludes that the use of fibre-bundling to improve toughness is unlikely to be effective due to the mechanism that has been proposed

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Vautey, Philippe. "Bilan des performances mécaniques des composites carbone/thermoplastiques pour l'aéronautique." Compiègne, 1993. http://www.theses.fr/1993COMP0639.

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Ce travail a été orienté pour dresser un bilan des performances mécaniques des composites à matrice thermoplastique, en s'efforçant d'identifier les sollicitations élémentaires sur lesquelles sont basées les sélections matériaux, pour un concepteur de structures aéronautiques. Le composite thermoplastique APC2/AS4 de la société ICI a servi de support à cette étude. Au delà d'une comparaison thermoplastique/thermodurcissable, l'influence d'une matrice ductile sur les propriétés des stratifiés a pu être étudiée grâce à l'APC2, qui se démarque nettement des systèmes thermodurcissables plus fragiles utilisés en production à ce jour. Après que le comportement élasto-plastique marque de la matrice Peek au sein du composite ait été souligné, l'analyse des modes de ruines a permis de préciser les raisons du compromis mécanique réalisé sur stratifiés APC2 vis à vis de la traction, de la compression, et de la sensibilité aux dommages d'impact et à l'environnement. Parallèlement, des aspects spécifiques à la morphologie semi-cristalline de ce thermoplastique ont été étudiés. Des conditions limites de moulage ont été proposées pour éviter certains risques de fragilisation.

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Huang, Da. "Structural behaviour of two-way fibre reinforced composite slabs." University of Southern Queensland, Faculty of Engineering and Surveying, 2004. http://eprints.usq.edu.au/archive/00001450/.

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Innovative new flooring systems utilising lightweight fibre reinforced polymer composite materials may have the significant potential to offer both economic and performance benefits for infrastructure asset owners compared to conventional concrete and steel systems. Over recent years, a range of prototype floor systems using fibre reinforced polymer composites have been developed by researchers at the University of Southern Queensland. However before such structural systems can be widely adopted by industries, fundamental understanding of their behaviour must be improved. Such work will allow for the development of new design and analysis procedures which will enable engineers to efficiently and accurately design and analyse such structures. This dissertation presents an investigation into a new two-way fibre reinforced composite floor slab system. The proposed new two-way slab system is, in essence, a sandwich structure with an innovative hollow core made from a castable particulate filled resin system. The key focus of this dissertation is the development of a new analysis tool to analyse the two-way fibre reinforced composite slab and facilitate subsequent parametric studies into slab configurations for concept refinement. The detailed 3D finite element analyses and experimental investigations are performed to verify the new analysis tool, and provide more detailed insight into the structural behaviour of this new two-way fibre reinforced composite slab. Comparisons with detailed 3D FEA and experiments illustrate that the simplified analysis tool is capable of providing sufficient accuracy for the preliminary analysis of a slab structure. Moreover, the 3D finite element analyses agree well with the experiments, and it is concluded that the behavioural responses of the proposed new slab structure can be reliably predicted. The experimental results show that this new slab concept exhibits quite a robust static behaviour and is likely to have a robust fatigue performance.

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Badripour, Yousef. "Characterization of Fibre Reinforcements for Non-structural Composite Parts." Thesis, Université d'Ottawa / University of Ottawa, 2018. http://hdl.handle.net/10393/38430.

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Fibre reinforced composite materials have attracted attention from industry and academia due to their high specific stiffness and strength. Commonly used manufacturing processes include the Liquid Composite Moulding (LCM) group of processes, where a liquid polymer resin impregnates a dry preform that is prepared in advance. The consistency of the resin infusion process and properties of the final composite are highly dependent on preform quality and reproducibility. Preform quality, in turn, depends on a process called draping. This work aims at understanding and developing quantitative knowledge of key elements of reinforcement behaviour during preforming. Testing characterization methods for dry fabrics are introduced and discussed. Moreover, the thesis probes relations between fabric properties such as their architecture and fibre type, and elements of their draping and preforming behaviour such as bending stiffness and in-plane shear properties of the dry fabrics. Most materials used in this work were selected by the industrial partner, Hutchinson Aerospace and Industry, based in Montreal. Some experiments were conducted using Hutchinson’s characterization devices, which are introduced in the relevant chapters.

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Benethuilière, Thibaut. "Phénomènes physico-chimiques aux interfaces fibre/matrice dans des composites SMC structuraux : Du mouillage à l'adhésion." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEI151.

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Musa, Corentin. "Élaboration et caractérisation de matériaux composites biosourcés à base de mucilage et de fibres de lin." Thesis, Littoral, 2019. http://www.theses.fr/2019DUNK0535.

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Les travux de thèse ont été menés dans un contexte de développement et de valorisation de la filière lin au travers de l'élaboration de nouveaux matériaux composites biosourcés à base de mucilage et de fibres de lin. Ces travaux ont conduit dans un premier temps à la synthèse de précurseurs d'isosorbide époxy et polyuréthanes comme alternative aux précurseurs toxiques conventionnels. Pour cela nous avons proposé une voie originale d'optimisation de la synthèse de diglycidyle éther d'isosorbide (DGEI) en utilisant un procédé ultrasonique. Par la suite, la comparaison des méthodes de transformation des époxys en carbonates cycliques par l'inclusion de CO₂ nous a servi de base dans l'élaboration d'un protocole efficace de conversion des DGEI en cyclocarbonates d'isosorbide (CCI) dans des conditions douces de pression et de température. Dans une seconde partie, l'extraction de composés hydrosolubles de la graine de lin a permis d'identifier la structure complexe du mucilage et les effets des paramètres d'extraction sur les propriétés physico-chimiques et thermiques du mucilage. Ensuite, pour la première fois, l'oxydation du mucilage au 2,2,6,6-tétraméthylpipéridine-1-oxyle (TEMPO) a été réalisée avec succès. Puis, nous avons pu mettre en évidence l'efficience de l'oxydation assistée par ultrasons comparée à la méthode classique lors de la montée en échelle du procédé. En vue d'améliorer la compatibilité fibre/matrice des composites à fibres végétales, des traitements appliqués sur des fibres courtes de lin ont été effectués amenant à l'individualisation des fibres et à l'amélioration de l'oxydation appliquée sur des fibres sonifiées. Ces différents matériaux ont permis de formuler un panel de nouveaux biocomposites. Les DGEI ont été valorisés par la confection d'une résine réticulée par une amine renforcée par des fibres longues de lin dont les performances sont identiques aux composites pétro-sourcés. Par la suite, la sonicationdes fibres courtes de lin a mené à l'amélioration des propriétés mécaniques de composite PLA/Lin. L'utilisation de mucilage oxydé a démontré les aspects positifs de l'incorporation du mucilage de lin dans les composites légers et résistants en compression The thesis was carried out in a context of development and valorisation of the flax through the conception of new bio-based composite materials made of mucilage and flax fibres. This work initially led to the synthesis of isosorbide epoxy and polyurethane precursors as an alternative to the conventional toxic precursors. For this, we proposed an original route for optimizing the synthesis of isosorbide diglycidyl ether (DGEI) using an ultrasonic process. Subsequently, the comparison of the conversion methods of epoxies into cyclic carbonates by the inclusion of CO₂ served as a basis for the development of an efficient protocol for converting DGEI into isosorbide cyclic carbonates (CCI) under moderate conditions of temperature and pressure. In the second part, the extraction of water-soluble compounds from the flaxseed allowed us to identify the complex structure of the mucilage and the effects of the extraction parameters on its physicochemical and thermal properties. Then, for the first time, oxidation of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) mucilage was successfully performed. After that, we have highlighted the enhanced efficiency of ultrasonic assisted oxidation over the conventional method when scaling up the process. In order to improve the fibre/matrix compatibility of natural fibre-based composites, different treatments of short flax fibres led to the individualizationof the fibres and to the improvement of the oxidation of sonicated fibres.These new materials allowed to formulate a series of novel biocomposites. The DGEI have been enhanced by making an amine-crosslinked resin reinforced with long flax fibres which have a comparable performance to oil-based composites. Additionally, the sonication of short flax fibres led to the improvement of the mechanical properties of PLA/Flax composite. The use of oxidized mucilage has demonstrated the beneficial aspects of flax mucilage incorporation into lightweight, compression-resistant composites

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Buggy, Stephen J. "Composite material process monitoring using optical fibre grating sensors." Thesis, Cranfield University, 2008. http://hdl.handle.net/1826/4035.

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In this thesis a long period grating (LPG) based sensor is investigated as a possible alternative to current process monitoring sensors used in the manufacture of composites to monitor cure. An LPG is demonstrated as a means of monitoring the cure of a UVcured epoxy resin. The wavelength shift of the attenuation bands were measured during the cure of the resin and compared with measurements made using a fibre optic Fresnel based refractometer. The results showed a good correlation (6 x 10 -3 rius) and illustrate the potential of the techniques for non-invasive composite material cure monitoring. Alternative fibre grating methods; a chirped LPG sensor, an in-fire Mach-Zehnder interferometer and a tilted fibre Bragg grating sensor, are also presented to demonstrate the versatility of grating based sensors for flow, high sensitivity refractive index and multi-parameter sensing, respectively. Demonstrations of LPG sensors in industrial applications are also presented and highlight the technical issues of integrating such devices in composite components and composite manufacturing processes.

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Humphreys, Matthew. "Development and Structural Investigation of Monocoque Fibre Composite Trusses." Queensland University of Technology, 2003. http://eprints.qut.edu.au/15898/.

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Fibre composite materials are gaining recognition in civil engineering applications as a viable alternative to traditional materials. Their migration from customary automotive, marine, aerospace and military industries into civil engineering has continued to gain momentum over the last three decades as new civil engineering applications develop. The use of fibre composite materials in civil engineering has now evolved from non-structural applications, such as handrails and cladding, into primary structural applications such as building frames, bridge decks and concrete reinforcement. However, there are issues which are slowing the use of fibre composite materials into civil engineering. Issues include high costs, difficulties in realising potential benefits, general lack of civil engineers' familiarity with the material and relatively little standardisation in the composites industry. For composites to truly offer a viable alternative to traditional construction materials in the civil engineering marketplace, it is essential that these issues be addressed. It is proposed that this situation could be improved by demonstrating that potential benefits offered by composites can be achieved with familiar civil engineering forms. These forms must be well suited to fibre composite materials and be able to produce safe and predictable civil engineering structures with existing structural engineering methods. Of the numerous structural forms currently being investigated for civil engineering applications, the truss form appears particularly well suited to fibre composites. The truss is a familiar structural engineering form which possesses certain characteristics that make it well suited to fibre composite materials. In this research a novel monocoque fibre composite truss concept was developed into a working structure and investigated using analytical and experimental methods. To the best of the author's knowledge the research presented in this thesis represents the first doctoral research into a structure of this type. This thesis therefore presents the details of the development of the monocoque fibre composite (MFC) truss concept into a working structure. The developed MFC truss was used as the basis for a detailed investigation of the structural behaviour of the MFC truss elements and the truss as a whole. The static structural behaviour of the principal MFC truss elements (tension members, compression members and joints) was investigated experimentally and analytically. Physical testing required the design and fabrication of a number of novel test rigs. Well established engineering principles were used along with complex finite element models to predict the behaviour of the tested truss elements and trusses. Results of the theoretical analysis were compared with experimental results to determine how accurately their static structural behaviour could be predicted. It was found that the static structural behaviour of all three principal truss elements could be accurately predicted with existing engineering methods and finite element analysis. The knowledge gained from the investigation of the principal truss elements was then used in an investigation of the structural behaviour of the MFC truss. Three full-scale MFC trusses were fabricated in the form of conventional Pratt, Howe and Warren trusses and tested to destruction. The investigation included detailed finite element modelling of the full-scale trusses and the results were compared to the full-scale test results. Results of the investigation demonstrated that the familiar Pratt, Howe and Warren truss forms could be successfully manufactured with locally available fibre composite materials and existing manufacturing technology. The static structural behaviour of these fibre composite truss forms was accurately predicted with well established engineering principles and finite element analysis. A successful marriage between fibre composite materials and a civil engineering structure has been achieved. Monocoque fibre composite trusses have been developed in the familiar Pratt, Howe and Warren truss forms. These structures possess characteristics that make them well suited to applications as primary load bearing structures.

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47

Kennedy, Gaylene Denise. "Repair of cracked steel elements using composite fibre patching." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0005/MQ34384.pdf.

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48

Nikoukar, Zanjani Farzad. "Strengthening of metallic structures using carbon fibre composite plates." Thesis, University of Southampton, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.404028.

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49

Waite, S. R. "Optical fibre witnesses of fatigue damage in composite materials." Thesis, City University London, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384019.

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50

Prichard, Jonathan Clive. "Post-impact compression behaviour of continuous fibre composite materials." Thesis, Queen Mary, University of London, 1991. http://qmro.qmul.ac.uk/xmlui/handle/123456789/1874.

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Compression-after-impact testing is widely used to assist in the development and selection of materials for aircraft applications. Presently, there are no standard test methods in existence. The most widely used industrial tests require large specimens which are expensive to manufacture and test. The results of an experimental study of the compression-after-impact test are reported. A miniaturised testing arrangement was used to investigate the effects of specimen width, thickness and lay-up on the measured compression strength of undamaged and impact damaged specimens. A toughened carbon I epoxy was used for the above work. In addition three other materials were tested (a carbon / polyetheretherketone (APC), a glass I epoxy (GRP) and another carbon / epoxy). The in-plane extent of delamination damage after impact was measured using an ultrasonic C-scanning method. The carbon and glass reinforced epoxy materials had similar resistance to the initiation and propagation of impact damage. The APC was much more resistant to the formation of impact damage. The measured strength of undamaged specimens was dependent upon specimen geometry, decreasing with width increase and increasing with thickness increase. The strength of impact damaged specimens was independent of width. Increasing the thickness increased the incident impact energy required to initiate damage and, therefore, delayed the onset of residual strength reductions. The strength of undamaged quasi-isotropic and 0/90 laminates was very similar and higher than for ±45 laminates. After impact the 0/90 material was strongest. The residual strength of the quasi-isotropic and ±45 materials were very similar. The APC retained the highest proportion of its initial strength over a range of incident impact energies. This was attributed to its resistance to the formation of impact damage. The GRP was the most damage tolerant material.

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Dissertations / Theses on the topic 'Fibre composite'

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