Dissertations / Theses on the topic 'Fibre reinforcements'
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Wretfors, Christer. "Hemp fibre and reinforcements of wheat gluten plastics /." Alnarp : Dept. of Agriculture - Farming Systems, Technology and Product Quality, Swedish University of Agricultural Sciences, 2008. http://epsilon.slu.se/11236319.pdf.
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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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Somashekar, Arcot Arumugam. "Compression deformation of glass fibre reinforcements in composites manufacturing processes." Thesis, University of Auckland, 2009. http://hdl.handle.net/2292/5579.
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Whole document restricted until 06/2011, see Access Instructions file below for details of how to access the print copy.Glass fibre reinforced polymer (GFRP) composites find application in diverse industries such as aerospace, marine, automotive, infrastructure and sport. GFRP composite products can be manufactured by a variety of methods, including the commonly employed Liquid Composite Moulding (LCM) group of techniques. Whatever the method, compression of the fibrous reinforcement is usually necessary in its natural dry state, and depending upon the technique, also after injection of a polymeric resin into a mould containing the reinforcement. A good understanding of the compression deformation behaviour of the reinforcement aids development of better models to describe and predict the manufacturing process, evaluate stresses acting on the mould, mould clamping and tooling forces required, and improvement of finished product quality. LCM models commonly assume non-linear elastic deformation of the fibre reinforcement network, while some also take into account viscoelastic behaviour. Earlier investigations demonstrated reinforcement stress relaxation under constant compressive strain. Reinforcements under loading (compaction) and unloading (release) follow different paths for the two phases. These phenomena indicate viscoelastic behaviour. Cyclic loading and unloading of reinforcements show a progressive shift of the fibre volume fraction - compression stress curve, signifying non-recoverable strain. This research further investigated these complex compression deformation phenomena which are not normally considered for modelling simulations. A series of experiments were conducted on glass fibre reinforcements of different architecture to determine and quantify in order of importance, different components of compression deformation. Permanent deformation was found to occur in all cases, and is comparable in magnitude to the elastic deformation of the reinforcement. Permanent deformation of the reinforcement considerably increased after just a few cycles of repeated compression and release. Time-dependent recovery of deformation on release of the compaction strain was found to largely depend on the number of layers of material in Continuous Filament Random Mat and Plain Weave Fabric reinforcements, it being of significant magnitude only with Plain Weave Fabric. A five component Maxwell-based model was developed to help explain and predict stress relaxation in the reinforcements under constant compressive strain. II III X-ray micro-computed tomography (micro-CT) scanning and imaging technology was utilised to investigate fibre reinforcement deformation in manufactured composite laminates. It was hypothesised that permanent deformation in Biaxial Stitched Fabric and Plain Weave Fabric reinforcements occurs by means of changes to fibre bundle cross-sections, while time-dependent recovery of deformation on release of the compaction strain is related to the undulations of fibre bundles in the direction of loading, and also to the tow crimp in the case of Plain Weave Fabric reinforcements. Analysis of the micro-CT images proved correct the hypothesis in the case of Continuous Filament Random Mat, while there was support for Plain Weave Fabric. It was also proposed that permanent deformation in Continuous Filament Random Mat reinforcements is via filament bending and displacement, while time-dependent recovery of deformation is based on filament – filament interactions. In this case CT scanning images provide some support towards understanding filament spread but more information is needed to conclusively prove the hypothesis.
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Ajayi, Olufemi. "The effect of fibre reinforcements on the mechanical behaviour of railway ballast." Thesis, University of Southampton, 2014. https://eprints.soton.ac.uk/372762/.
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Ballast is a primary component of the railway track and it has several functions including the ability to resist vertical, lateral and longitudinal forces applied to the sleepers from the train wheels. In response to the stresses induced during a train passage, ballast typically experiences plastic settlement which can reach unacceptable magnitudes. Thus, ballast is the focus of the majority of maintenance and renewal activities. In response to the growing need for resilient track materials (including ballast) to cope with increasing train speed, load and frequency, means of optimizing its performance and minimizing maintenance requirements are required. Ballast improvement techniques, such as the use of geogrids, have attracted a great deal of attention in terms of research, but huge potential for reducing costs through ballast improvement still exist. It has been shown from previous research that the use of randomly oriented fibres in sands can significantly improve their strength. This technique might be used to improve ballast strength and reduce track geometry deterioration. In addition, fibre reinforcements in ballast can potentially provide a new method of reinforcing ballast whilst maintaining the capability of withstanding typical tamping operations which are incompatible with geogrids. However, there is a lack of rigorous scientific understanding of the effects of fibre reinforcements on relatively large aggregates such as railway ballast. This research examines the effect of random fibre inclusions on the packing structure of granular materials (coarse sand and scaled ballast) and describes the physical implications associated with the observed changes. The mechanical properties of fibre reinforced granular materials across different particle sizes and a hypothesis of fibre/particle reinforcement suitable for relatively large particles are presented. An image-based deformation measurement technique has also been used to investigate the effects of fibre reinforcements on the local deformation of triaxial specimens to corroborate the observed mechanical behaviour of the reinforced specimens. Finally, the mechanical behaviour of a fibre reinforced ballast layer below a cyclically loaded railway sleeper was investigated using a full scale laboratory tests.
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D'Agostino, Marco Valerio. "Generalized continua and applications to finite deformations of quasi-inextensible fiber reinforcements." Thesis, Lyon, INSA, 2015. http://www.theses.fr/2015ISAL0061/document.
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La microstructure des matériaux constitue un outil essentiel pour optimiser les propriétés mécaniques des structures et ainsi améliorer leurs performances. Les modèles de Cauchy ne sont pas toujours adaptés à la description de la réponse dynamique de certains matériaux microstructurés montrant des comportements mécaniques exotiques. Les théories de milieux continus généralisés peuvent être de bonnes candidates pour modéliser ces matériaux d’une façon plus précise et plus réaliste, aussi bien en statique qu’en dynamique, puisqu’elles peuvent décrire, même d’une façon simplifiée, la manifestation macroscopique de la présence d’une microstructure. Ce manuscrit est organisé comme suit : - Dans le chapitre 1 nous introduisons les aspects généraux de la mécanique des renforts fibreux.- Dans le chapitre 2 nous rappelons certains concepts fondamentaux concernant la mécanique des milieux continus classiques. De plus, nous introduisons les théories de deuxième gradient à l’aide du Principe des Travaux Virtuels.- Dans le chapitre 3 nous nous proposons de présenter une première modélisation des renforts fibreux de composites en mettant en place des modèles numériques discrets. Cette modélisation discrète permet de rendre compte de certains effets de la microstructure des renforts fibreux sur leur comportement macroscopique global. En particulier, il sera montré que la flexion locale des mèches à l’échelle mesoscopique a un effet non-négligeable sur le comportement macroscopique global de ces matériaux. Dans un deuxième moment nous introduisons une modélisation continue de deuxième gradient pour la description des mêmes matériaux et nous montrons que les termes d’ordre supérieur permettent une description satisfaisante des effets de flexion locale sur-cités.- Dans le chapitre 4 on particularise le cadre général de la mécanique des milieux continus introduit dans le chapitre 2 au cas particulier des milieux continus 2D. On mettra un accent fort sur l’interprétation géométrique des mesures de déformation de deuxième gradient qui seront directement reliées aux courbures dans le plan de certaines lignes matérielles. Ces lignes matérielles seront ensuite interprétées dans les chapitres suivantes comme décrivant les mèches des renforts fibreux de composites qu’on se propose d’étudier.- Dans le chapitre 5 nous introduisons une hypothèse cinématique forte sur les déformations admissibles, en supposant que les mèches du renfort considéré sont inextensibles. Cette hypothèse nous permettra de construire un modèle simplifié de premier gradient pour le comportement des renforts de composites 2D qui est encore représentatif de leur comportement mécanique. Une méthode numérique permettant de montrer certaines solutions concernant le cas du bias extension test est codée en Mathematica et les résultats obtenus sont discutésDered materials in the simplest and more effective way. However, there are some cases in which the considered materials are heterogeneous even at relatively large scales and, as a consequence, the effect of microstructure on the overall mechanical behavior of the medium cannot be neglected. In such situations, Cauchy continuum theory may not be useful to fully describe the mechanical behavior of considered materials. It is in fact well known that such continuum theory is not able to catch significant phenomena related to concentrations of stress and strain and to specific deformation patterns in which high gradients of deformation occur and which are, in turn, connected to particular phenomena which take place at lower scales. Generalized continuum theories may be good candidates to model such micro-structured materials in a more appropriate way since they are able to account for the description of the macroscopic manifestation of the presence of microstructure in a rather simplified way. The present manuscript is organized as follows: In ch.1 a general description of fibrous composite reinforcements is given. In ch.2 some fundamental issues concerning classical continuum mechanical models are recalled. In ch.3 we start analyzing some discrete and continuum models for the description of the mechanical behavior of 2D woven composites. At this stage of the manuscript, we want to show how some discrete numerical simulations allowed us to unveil some very special deformation modes related to the effect of the local bending of fibers on the overall macroscopic deformation of fibrous composite reinforcements. Such discrete simulations showed rather clearly that microscopic bending of the fibers cannot be neglected when considering the deformation of fibrous composite reinforcements. For this reason, we subsequently introduced a continuum model which is able to account for such microstructure-related effects by means of second gradient terms appearing in the strain energy density. In ch.4 we reduce the general continuum mechanical framework introduced in ch.2 to the particular case of 2D continua. In ch.5 we introduce a strong kinematical hypothesis on the admissible deformations, assuming that the yarns composing the woven reinforcements are inextensible
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Rajpurohit, Ashok. "Development of advanced carbon/glass fibre based hybrid composites." Thesis, Université Paris sciences et lettres, 2020. http://www.theses.fr/2020UPSLM020.
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Les composites hybrides offrent un moyen efficace d'améliorer les propriétés mécaniques des matériaux composites. Cette thèse vise à comprendre le comportement mécanique et l'effet synergique offerts par de tels composites hybrides sous plusieurs conditions de chargement. L'accent est mis, non seulement sur la caractérisation mécanique, mais également sur le développement et l'optimisation de nouvelles générations de renforts hybrides, permettant ainsi une hybridation aussi bien au niveau des nappes, qu’au niveau des mèches et des fibres. Dans ce travail, les fibres de carbone et de verre sont choisies comme les deux types de renforts pour les composites hybrides. Les propriétés de ces fibres unitaires sont d'abord caractérisées pour étudier l'impact des procédés textiles. De nouveaux renforts unidirectionnels ont été fabriqués après avoir optimisé les procédés, tels que la technologie UD cousu et l'étalement des fibres. Les composites ont été fabriqués via RTM basse pression en utilisant une résine époxy. Les caractéristiques en raideur et en résistance des composites de référence, des hybrides inter-plis, intra-plis et fibre à fibre ont ensuite été caractérisées dans des conditions de charge quasi-statique en traction, compression et flexion. L'effet d’hybridation (synergique) a été évalué pour ces composites en comparant les propriétés du composite hybride avec un composite de référence en carbone. Afin de comprendre le comportement à rupture de ces composites dans différentes conditions de charge, une étude de fractographie a été réalisée. Les hybrides inter-plis font apparaître une légère augmentation de la déformation à rupture en traction mais présentent une synergie négative pour toutes les autres conditions. Les hybrides intra-plis montrent eux, un effet synergique pour les résistances à la traction et à la compression, sans réduire leur déformation à rupture. Un composite hybride fibre à fibre réalisé par étalement montre une performance mécanique supérieure par rapport à d'autres hybrides. Les résultats présentés révèlent les avantages potentiels de l'hybridation à différents niveaux et dispersions. Les résultats ouvrent une voie pour les futurs travaux sur les composites hybrides et leurs procédésHybrid composites offer an effective way of enhancing mechanical properties of composite materials. This thesis aims to understand the mechanical behaviour and synergistic effect offered by such hybrid composites in several loading conditions. The focus not only lies on mechanical characterisation but also on development and optimization of new generation of hybrid reinforcements thus allowing hybridization both at ply levels and at tow and fibre levels. In this work, carbon and glass fibres are chosen as the two types of reinforcements for hybrid composites. Single fibre properties of these fibres were first characterised to study the effect of textile processes. Novel unidirectional reinforcements have been fabricated after optimising the processes such as unidirectional stitching and spreading technology. Composites were manufactured via low pressure RTM process using an epoxy resin. Stiffness and failure characteristics of reference, interply, intraply and intermingled hybrid composites were then characterised in quasi-static tensile, compression and flexural loading conditions. The hybrid (synergistic) effect were evaluated for these composites by comparing the hybrid composite properties with a carbon reference composite. To understand the failure behaviour under different loading conditions, a fractography study was conducted. Interply hybrids slightly increase the failure strain in tension but demonstrate negative synergy in all other properties. On the other hand, intraply hybrids show a synergistic effect in both tensile and compressive strengths, while not reducing the failure strain. A spread tape intermingled hybrid composite demonstrates a superior mechanical performance when compared to other hybrids. The presented results reveal the potential benefits of hybridisation at different levels and dispersions. The results provide a driving force for future work on hybrid composites and their processing
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Bassoumi, Amal. "Analyse et modélisation du choix des renforts pour optimiser la mise en forme de matériaux composites à base de fibres végétales." Thesis, Orléans, 2016. http://www.theses.fr/2016ORLE2053.
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Cette thèse s’inscrit à mi-chemin entre l’étude de la déformabilité des structures tissées et la valorisation de la fibre de lin pour des applications dans le renforcement des matériaux composites. Le premier objectif de l’étude est de caractériser expérimentalement le comportement en flexion des mèches de différentes structures constituées de fibres de lin ainsi que des tissus de différentes armures. Les travaux ont abordé aussi des paramètres tels que l’humidité relative et la composition (des mèches comélées ou en lin pure). Le deuxième objectif des travaux est d’étudier le comportement en flexion des tissus en fonction du comportement en flexion des mèches. Cette partie a commencé par la modélisation géométrique des renforts tissés dans le but de suivre l’évolution de la section du tissu qui varie dans la direction de la flexion. La modélisation mésoscopique a permis de calculer analytiquement les propriétés géométriques du tissu en particulier son moment quadratique. Les résultats obtenus ont été utilisés dans la simulation de la flexion du tissu. L’étude a permis de voir jusqu’à quel point le comportement de la mèche et le moment quadratique du tissu pilotent le comportement en flexion du tissu. D’après ces travaux, le comportement en flexion du tissu semble être approché de façon satisfaisante sur toute la gamme de longueurs envisagées à partir de ces deux grandeurs sauf pour les forts taux d’humidité où d’autres phénomènes doivent être considérés. L’étude a souligné que la différence entre deux renforts testés expérimentalement peut être anticipée numériquement. Ainsi, le concepteur de tissus sera capable d’anticiper la rigidité expérimentale du tissu pour faire des tissages adaptés à la mise en forme du renfort. Une étude paramétrique de la flexion a été également réalisée dans le but de déduire les paramètres les plus influents sur lesquels il peut jouerThis thesis is halfway between the study of the deformability of woven structures and the use of flax fibre as reinforcement of composite materials. The first aim of the study is the experimental characterization of the bending behaviour of tows with different structures made of flax fibres and fabrics with different weaves. Parameters such as relative humidity and the composition (100% flax and commingled tows) were also considered. The second aim of the study is to link the bending behaviour of the fabric to the bending behaviour of its constituent tows. This part starts with the geometric modelling of woven fabrics in order to follow the variation of its section in the bending direction. Mesoscopic modelling allows the analytical calculation of the geometric properties of the fabric in particular its moment of inertia. The results obtained were used in the simulation of the fabrics bending to see how far the behaviour depends on the tows bending behaviour and the moment of inertia. The bending behaviour of the fabric seems to be approached satisfactorily from these two factors. This is verified within the range of lengths considered except for high humidity (in this case, other phenomena must be considered). The study pointed out that the difference between two reinforcements tested experimentally can be predicted numerically. Thus, the fabrics designer will be able to anticipate the experimental bending stiffness of the fabric in order to adapt the weaving to the shape forming. A parametric study of the bending was also achieved in order to deduce the most influential parameters of the fabric for an appropriate weaving
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Huang, Jin. "Simulation du drapage des renforts de composites multicouches liés par piquage." Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEI098.
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De nos jours, les matériaux composites permettent de diminuer la masse des pièces et sont largement utilisés dans le domaine de l'aérospatial, de l'aéronautique et de l'automobile. De plus, les composites multicouches à renfort textiles permettent de la conception des structures épaisses telles que les aubes de la soufflante des réacteurs d'avion. Cependant, de nombreux défauts peuvent apparaître pendant le processus de mise en forme des renforts multicouches, comme des plissements. Des recherches sur la formation de plis, ainsi que sur la technique de piquage pour améliorer la propriété mécanique des renforts multicouches dans l'épaisseur sont présentées dans ce travail. La première partie de ce présent rapport consiste à étudier la formation de plis des renforts multicouches soumis à la flexion hors plan. Dans un premier temps, l'influence des différentes orientations des couches sur la formation de plis est explorée. La relation entre le chargement appliqué sur le tissu et la création de plissements est ainsi montrée. Le second chapitre consiste à comparer l'influence de deux types de tissage pour ce qui concerne la drapabilité du composite. La troisième partie propose deux modèles numériques adaptés pour simuler le drapage des renforts composites liés par piquage. Ces approches impliquent l'utilisation d'un élément fini de coque de type stress resultant pour représenter chaque couche de renfort et des éléments de barre pour représenter le fil de piquage. Ces modèles nécessitent un algorithme de contact propre pour gérer l'interaction entre le renfort et le fil de piquage. Enfin, la dernière partie consiste à valider les modèles par une comparaison entre les simulations et les essais expérimentauxNowadays, composite materials make it possible to reduce the mass of parts and are widely used in the aerospace, aeronautics and automotive industries. In addition, the multilayered reinforcement of composites allows the design of thick structures such as the fan blades of aircraft engines. However, many defects can occur during the forming process of multilayered reinforcements, such as the wrinkling problem. Research on the formation of wrinkles, as well as on the tufting technology to improve the mechanical property of multilayered reinforcements in the direction of thickness are presented in this work. The first part of this report is a study of the formation of the wrinkles of multilayered reinforcements subjected to out-of-plane bending. Firstly, the influence of the different orientations of the layers on the formation of wrinkles is explored. The relationship between the load applied to the fabric and the creation of wrinkles is thus shown. The second chapter compares two types of weaving pattern on the drapability of the composite. The third part consists of developing two numerical models adapted to simulate the forming of tuft-bonded composite reinforcements. These approaches involve the use of a stress resultant shell element to represent each layer of reinforcement and bar elements to represent the tufting yarn. These models require a specific contact algorithm to manage the interaction between the reinforcement and the tufting yarn. Finally, the last part consists of validating the models by comparing simulations and experiments
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Yang, Haomiao. "Study of a unidirectional flax reinforcement for biobased composite." Thesis, Normandie, 2017. http://www.theses.fr/2017NORMC226/document.
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Dans cette thèse, un composite unidirectionnel à renfort lin (composite UD biosourcé) a été développé et élaboré par la technique de presse à chaud. Le comportement en traction des composites à renfort végétal montre en général deux domaines, mais un troisième domaine est identifié dans ce travail. Un modèle phénoménologique développé précédemment pour décrire le comportement en traction d'un composite à renfort en fils torsadés a été testé avec le composite UD biosourcé. Nous montrons que l'ajout d'un phénomène de consolidation au modèle précédent est nécessaire pour simuler correctement le troisième domaine. Un second modèle mécanique a été par ailleurs développé pour identifier expérimentalement les propriétés mécaniques effectives du renfort en lin lorsqu'il est piégé dans la matrice. La distribution statistique de l'orientation locale du renfort a été mesurée pour pouvoir prendre en compte l'orientation des fibres. Pour cela, la technique du tenseur de structure a été appliquée sur des images optiques du pli de lin. Par ailleurs, ce modèle permet d'étudier l'influence des porosités sur les propriétés mécaniques. Les deux modèles permettent d'effectuer des prévisions efficaces du comportement mécanique du composite de fibre de lin unidirectionnel. En complément des modèles de mécanique, le comportement en sorption du composite de lin UD a également été analysé. Le modèle de Langmuir et le modèle de Fick ont été appliqués sur nos composites UD. Les résultats montrent que la configuration unidirectionnelle du renfort de lin favorise la sorption d'eau des composites associés.Résumé en anglaisIn this Ph.D work, unidirectional flax fiber composite (UD biobased composite) has been designed and manufactured based on the hot platen press process. Plant fiber composites usually exhibit two regions under tensile load, but three regions have been identified in this work. A phenomenological model, previously developed to describe the tensile mechanical behavior of twisted plant yarn composites, has been tested with the UD biobased composite. We show that the addition of a strengthening phenomenon to the previous model is necessary to simulate correctly the third region. A second mechanical model has also been developed for experimental identification of the effective mechanical properties of flax reinforcement when embeded in matrix. A statistical distribution of local orientation of UD reinforcement was obtained allowing taking the fiber orientation into account. To that end, structure tensor method was applied to optical images of flax ply. Furthermore, this model allows the effect of porosity on mechanical properties to be studied. Both models provide effective forecast of the mechanical behavior of unidirectional flax fiber composite. Besides the mechanic models, sorption behavior of UD flax composite also has been analyzed. Langmuir's model and Fick's model were applied on our UD composite. The results show that the unidirectional configuration of the flax reinforcement promotes the water sorption from the associated composites
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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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Fiorelli, Juliano. "Utilização de fibras de carbono e de fibras de vidro para reforço de vigas de madeira." Universidade de São Paulo, 2002. http://www.teses.usp.br/teses/disponiveis/88/88131/tde-12052003-144536/.
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A necessidade de recuperação e reforço em estruturas de madeira, concreto e aço exigiu da construção civil uma procura por métodos mais eficientes que pudessem cumprir esse papel. Com este objetivo vários estudos estão sendo realizados utilizando fibras reforçadas com polímeros (FRP). Dentre estas fibras, as que vêm apresentando melhores resultados como reforço para peças estruturais de madeiras são as fibras de carbono e as fibras de vidro. Dentro deste escopo, este trabalho tem como objetivo estudar o comportamento estrutural de vigas de madeira de espécies nacionais reforçadas com fibras de carbono e com fibras de vidro, verificando a eficiência deste reforço e adequando modelos de cálculo para avaliação da resistência e da rigidez das vigas reforçadas, e também verificar a eficiência de uma formulação de adesivos à base de mamona e do adesivo Cascophen, para fixação das respectivas fibras na madeira, em substituição ao adesivo epóxi, normalmente utilizado. Foram efetuados ensaios de vigas de madeira reforçadas com polímeros, em modelo reduzido, e em protótipos, para diversas configurações de geometria e quantidade de fibras utilizadas. Os resultados obtidos indicam uma boa concordância entre os modelos teóricos para avaliar a resistência e a rigidez das vigas reforçadas, e os resultados experimentais, e a eficiência do reforço. Também foram conduzidos ensaios de tração em corpos-de-prova de fibras laminado com os adesivos, caracterizando a sua resistência e elasticidade e comparando o comportamento dos adesivos estudados. Os resultados indicaram o melhor comportamento do adesivo epóxi.The necessity of rehabilitation and reinforcement in wood structures, concrete and steel demanded a search for more efficient methods that could to carry this paper. With this objectives several studies are using fibers reinforced polymers (FRP). These fibers which presenting better results in structural reinforcement for structural pieces of wood are the fibers of carbon and the glass fibers. This work has as objective studies the structural behavior of wood beams of national species reinforced with carbon fibers and with glass fibers, verifying the efficiency of this reinforcement and adapting calculation models for evaluation of the strength and stiffness of the reinforced beams, and also to verify the efficiency of a formulation of adhesives to the castor oil and of the adhesive Cascophen, for fixation of the respective fibers in the wood, in substitution the adhesive epoxy, usually used. Experimental work was made with wood beams reinforced with polymeric, in reduced model, and in prototypes, for several geometry configurations and amount of used fibers. The obtained results indicate a good agreement among the theoretical models to evaluate the strength and stiffness of the reinforced beams, and the experimental results, and the efficiency of the reinforcement. Traction rehearsals were also led in body-of-proof of fibers laminated with the adhesives, characterizing your strength and elasticity and comparing the behavior of the studied adhesives. The results indicated the best behavior of the adhesive epoxy.
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Zhang, Endang. "Fibre reinforcement of oxynitride glasses and glass-ceramics." Thesis, University of Newcastle Upon Tyne, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320017.
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Thomas, Jeff Scott. "Plastic fiber rolling for concrete reinforcement." Diss., Rolla, Mo. : University of Missouri-Rolla, 1996. http://scholarsmine.mst.edu/thesis/pdf/Thomas_09007dcc805b0f25.pdf.
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Thesis (M.S.)--University of Missouri--Rolla, 1996.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed November 24, 2008) Includes bibliographical references (p. 117-118).
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Whitehead, Paul Arthur. "Shear strength of concrete containing fibre-reinforced-plastic reinforcement." Thesis, University of Bath, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.275880.
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Pigg, W. "The fibre reinforcement of low density rigid polyurethane foam." Thesis, Manchester Metropolitan University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372751.
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Harris, Jonathan. "A preliminary study upon the use of novel shaped fibres for the through thickness reinforcement of continuous fibre reinforced plastics." Thesis, University of Bristol, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.428511.
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Pender, Kyle Robert. "Recycling, regenerating and reusing reinforcement glass fibres." Thesis, University of Strathclyde, 2018. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=30389.
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Over the last decades, the use of glass fibre reinforced thermosets (GRT) has become widespread and commonly used in many sectors. Currently no commercial recycling process exists for GRT and the amount of waste generated has reached an unsustainable level. The value of recycled glass fibres (RGF) is reduced significantly due to loss in strength and surface functionality during recycling. Thermal recycling processes involve decomposing the polymer matrix at elevated temperatures to recover the reinforcement fibres. Exposing to such high temperatures degrades the strength of the fibres as well as removes the sizing on the fibre surface. The focus of this thesis is to investigate the potential for retaining and regenerating the strength and interface properties of thermally recycled glass fibres; in order to produce composites reinforced with RGF that could complete with those using virgin/pristine glass fibres. In order to recycled GRT in-house, a lab scale thermal recycling system based on a fluidised bed reactor was initially designed and developed. To build on the already extensive research into this recycling process, this thesis aims to reduce the temperature required to recycle GRT within the fluidised bed by introducing a metal oxide catalyst to aid in the thermal decomposition of the thermosetting matrix. This novel line of research was selected due to the potential for reducing both the energy consumption of the recycling process and thermal damage sustained by the glass fibres during recycling. Using thermogravimetric analysis it was found that copper (II) oxide (CuO) was particularly active at catalysing the thermal decomposition of epoxy, reducing the decomposition temperature by up to 125 °C. When used within the fluidised bed recycling process, CuO facilitated recycling of glass fibre from glass fibre reinforced epoxy (GF-EP) at just 400 °C without compromising on fibre yield efficiency. Another avenue of research in this thesis was assessing the potential of a variety of chemical treatments to regenerate the strength and surface functionality of thermally recycled glass fibres. It was found that soaking in hot NaOH solution could provide approximately a 130% increase in the strength of RGF; concluding that changes to surface morphology due to etching was the re-strengthening mechanism. The interfacial adhesion between RGF and 1) polypropylene (PP) and 2) epoxy were examined. It was found that the interfacial shear strength (IFSS) between RGF and epoxy could be fully restored by first treating the RGF in NaOH solution. Regenerating the IFSS between RGF and PP proved more challenging despite the use of fibre sizing and PP matrix modification. GRP reinforced with RGF (with and without regeneration treatments) were prepare and mechanically characterised; however, the GRP exhibited significantly poorer mechanical properties than those prepared with virgin fibres. This drop in performance was typically attributed to a combination of 1) lower fibre strength, 2) poor fibre-polymer interfacial adhesion and 3) low fibre volume fraction within the GRP.
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Avril, Nicolas Joseph. "Manufacturing glass-fiber reinforcement for grinding wheels." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/38432.
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Shapiro, Nathan. "Optimal fiber yield strength for concrete reinforcement." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/38044.
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Silva, Vera. "Cost-effective Building Constructions – Carbon Fibres Reinforcement." Thesis, KTH, Byggnadsteknik, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-35085.
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Shehata, Emile F. G. "Fibre-reinforced polymer (FRP) for shear reinforcement in concrete structures." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0001/NQ41626.pdf.
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Jacobsson, Elin. "Environmental Impact Analysis of Flax Fibre Cultivation for Composite Reinforcement." Thesis, Mittuniversitetet, Avdelningen för ekoteknik och hållbart byggande, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-34881.
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Searching for environmentally sustainable alternatives for reinforcement of composite materials, flax fibre has one of the most promising potentials due to its desired mechanical properties. The fact that flax is a bio-material, in contrast to conventional synthetic fibres, does not ensure a less environmental impact. One of the major source of environmental impact related to flax fibre as a reinforcement material is the cultivation of flax fibre. In this study the environmental impact of flax fibre cultivation was studied by performing an environmental impact analysis with a life cycle assessment inspired approach. The result showed that the quantification of the environmental impacts varied to a large extent depending on several parameters such as allocation method and whether carbon sequestration was included in the calculations. One striking example is the results for global warming potential, ranging from 10 000 kg CO2-equivivalents to a negative value per 1 tonne of flax fibre. The study showed the production and use of fertilizers to be the major contribution to the environmental impact by as much as 70-90 %. In order to limit the environmental impact from flax fibre cultivation suggested environmental improvements are to optimise the fertiliser use according to the flax type and soil conditions, improving nitrogen fixation as well as using organic fertilizers.2018-06-27
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Weitzenböck, Jan Rüdiger. "Flow characterization in resin transfer moulding." Thesis, University of Southampton, 1996. https://eprints.soton.ac.uk/403475/.
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Simkins, Virginia R. "Auxetic polymeric fibres as potential reinforcements in composite materials." Thesis, University of Bolton, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.486105.
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Materials with negative Poisson's ratios (Le. those that expand in the transverse when tensile load is applied in the longitudinal) are also known as 'auxetic' materials. While there are examples of naturally occurring auxetic materials, the increasing interest in synthesising this property in various materials and at various levels of physical magnitude from nano-scale to macro-scale has led to increasing research over the past two decades. As well as elasticity theory, much theoretiCal modelling has shown the potential benefits of these materials in different situations, r' such as self-cleaning filters and molecular sieves, push-fasteners, medical bandages and sutures, smart textiles and energy-absorbing protective materials. One branch of auxetic research concentrates on the production of auxetic polymers at the microstructural level. The production of au;
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Grabovac, Ivan, and ivan grabovac@dsto defence gov au. "Composite Reinforcement for Naval Ships: Concept Design, Analysis and Demonstration." RMIT University. Applied Sciences, 2006. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20070209.151724.
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This thesis outlines the development of composite reinforcement technology for a ship's aluminium alloy superstructure. The work objective aimed to alleviate stress concentration in parts of the superstructure prone to fatigue-induced cracking. This is a novel approach to ship repair, which promises reduction in the cost of maintenance primarily due to greater efficiency and lower cost of repair. The work was conducted over approximately 12 years. It commenced in the late 80s with laboratory research and development and concluded in 2000 after completion of a seven-year trial on board a navy ship. Two carbon fibre composites, (5 m x 1 m consisting of a 25-ply laminate), were adhesively bonded to the 02-deck on the port and starboard sides. It was found that upgrading the structure using composites was effective, making it able to withstand service fatigue stresses. Finite element modelling and strain measurements on board the ship showed that critical stress concentration could be alleviated through stress redistribution. For the duration of the trial, no cracking of aluminium alloy deck in the vicinity of the reinforcements was reported. Both composite reinforcements exhibited good performance and remained in service after the end of the trial. However, the marine environment did cause some non-structural, edge debonding of the glass fibre reinforced overlay at the composite-metal interface. This overlay was designed to provide surface protection to the underlaying carbon reinforcement. Bond degradation was patchy. It occurred after about three years in service, most probably due to a combination of thermal cycling (solar heating/cooling) and water ingress at the interface. A new edge sealing method restored its durability and it required no further attention. This experiment was successfully demonstrated on board an active navy ship. The work proved that an effective and durable repair of a ship structure using non-metallic repair technology is feasible. Composite reinforcements prevented deck cracking and removed any need for welded repairs, thereby reducing the cost of ship maintenance. For further cost reduction it is recommended to adopt the principle of reverse engineering to simplify the technology for dockyard use.
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Mirzababaei, M. "Reinforcement of clay soils using waste carpet fibres." Thesis, University of Bolton, 2012. http://ubir.bolton.ac.uk/809/.
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It is reported that about 500,000 tonnes (i.e. 2% of the total waste) of waste carpet fibres are plunged into landfills annually in the UK. Municipalities and environmental authorities are increasingly concerned about the growing amount of carpet waste produced by household, commercial and industrial sectors. The notion of reusing such waste in industry has therefore attracted substantial attention in recent years by researchers and environmentalists. There have been a large number of studies in utilisation of virgin fibres in soils and other civil engineering applications. However, by contrast there have been relatively few studies of waste fibres especially waste carpet fibres in this context and in particular in cohesionless soils. In this study, the mechanical behaviour of composite cohesive soils (i.e. clay soils) with proportionate concentration of two types of waste carpet fibre is investigated. A series of consolidated undrained triaxial shear tests, Oedometer tests, swelling pressure tests and unconfined compression tests have been carried out to evaluate the effectiveness of the waste carpet fibres in improving the mechanical properties of cohesive clay soils including; shear strength and compression strength as well as reducing swelling pressure and consolidation settlement of such soils. The results have shown that waste carpet fibres do increase the shear strength and unconfined compression strength of clay soils proportional to fibre content. It was found that relative increase in unconfined compression strength or reduction in swelling pressure of the fibre reinforced clay soils is dependent on the initial dry unit weight and moisture content of the clay. A neural network analysis was conducted on the results of the triaxial shear tests to construct a predictive model for estimating the maximum deviator stress in consolidated undrained triaxial tests as a function of fibre type, fibre content, dry unit weight and consolidation pressure. The modelled behaviour was shown to be a perfect fit with the experimental data. Model slope tests were also carried out using a large scale laboratory test tank (L:800mm x W:300mm x H:500mm) to investigate the load bearing pressure of the slope made of fibre reinforced clay soil under strip footing load. The results confirmed that bearing pressure of the model slopes increased significantly with increased fibre content. Particle image velocimetry (PIV) method was used to track the displacement of the soil particles in the exposed front view of the model slope and contours of displacement and slip surfaces of the model slopes were determined and compared.
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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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Hajsadeghi, M. "Engineered structural fibres as replacement for traditional reinforcements for concrete." Thesis, University of Liverpool, 2018. http://livrepository.liverpool.ac.uk/3021280/.
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Brennan, Kelly Patrick. "Numerical multi-scale resin infiltration modeling of unidirectional fiber reinforcements." Laramie, Wyo. : University of Wyoming, 2008. http://proquest.umi.com/pqdweb?did=1633772951&sid=1&Fmt=2&clientId=18949&RQT=309&VName=PQD.
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Palmer, James Alexander Thomas. "Mechanical recycling of automotive composites for use as reinforcement in thermoset composites." Thesis, University of Exeter, 2009. http://hdl.handle.net/10036/72313.
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The aim of this research was to investigate the potential use of recycled glass fibre composite materials as a replacement for virgin reinforcing materials in new thermoset composites. Specifically the closed-loop mechanical recycling of composites used heavily in the automotive sector known as dough and sheet moulding composites, DMC and SMC respectively, are investigated. The recycling of glass reinforced thermoset polymer composite materials has been an area of investigation for many years and composites used in the automotive industry are of particular interest due to legislative and social pressures on the industry. The mechanical recycling process and then collection of useful fibrous grades of recycled materials, recyclate, by a novel air separation technique were investigated first. The properties of these recyclate fibres were characterised and compared directly with the properties of virgin glass fibres they were to be used to replace. Single fibre tensile tests were employed to compare the strengths of the fibres and single fibre pull-out tests were used to investigate the strength of the interface between the fibres and a polyester matrix. These tests showed the recyclate fibres to be weaker and have a poorer interface with the polyester matrix than the virgin glass fibres. Understanding the properties of the recyclate materials meant their reformulation into new composites could be carefully considered for the production of new high performance materials. Two grades of the collected recyclate materials were then reformulated in to new DMC and SMC composites, replacing percentages of the virgin glass fibre reinforcement. The mechanical properties of the resulting manufactured composites were characterised throughout for direct comparison against one another and an unmodified control material, using both three-point flexural tests and Charpy impact tests. Through the modification of existing manufacturing techniques and the development of novel production equipment it has been possible to successfully manufacture both DMC and SMC composites with the recyclate materials used to replace virgin glass fibres. Virgin glass fibres have successfully been replaced by recyclate materials without disrupting standard production techniques and with minimal reduction of the mechanical properties of the resulting composites. As the loadings of recyclate materials used were greatly increased both the flexural and impact strengths were significantly degraded and it was found that chemical modification of the composite could be used to improve these formulations. It has been shown that the recyclate materials should be considered and treated as a distinct reinforcing ingredient, separately from the remaining virgin glass fibres.
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Levchuk, Svetlana. "Interface development for a EUROFER steel matrix composite with SiC-fibre reinforcement." [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=97895694X.
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Mondo, Eleonora. "Shear Capacity of Steel Fibre Reinforced Concrete Beams without Conventional Shear Reinforcement." Thesis, KTH, Bro- och stålbyggnad, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-41016.
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While the increase in shear strength of Steel Fibre Reinforced Concrete (SFRC) is well recognized, it has yet to be found common application of this material in building structures and there is no existing national standard that treats SFRC in a systematic manner. The aim of the diploma work is to investigate the shear strength of fibre reinforced concrete beams and the available test data and analyse the latter against the mostpromising equations available in the literature. The equations investigated are:Narayanan and Darwish’s formula, the German, the RILEM and the Italian guidelines. Thirty articles, selected among over one hundred articles taken from literature, have been used to create the database that contains almost 600 beams tested in shear. This large number of beams has been decreased to 371 excluding all those beams and test that do not fall within the limitation stated for this thesis. Narayanan and Darwish’s formula can be utilized every time that the fibre percentage, the type of fibres, the beam dimensions, the flexural reinforcement and the concrete strength class have been defined. On the opposite, the parameters introduced in the German, the RILEM and the Italian guidelines always require a further characterization of the concrete (with bending test) in order to describe the post‐cracking behaviour. The parameters involved in the guidelines are the residual flexural tensile strengths according to the different test set‐ups. A method for predicting the residual flexural tensile strength from the knowledge of the fibre properties, the cylindrical compressive strength of the concrete and the amount of fibres percentage is suggested. The predictions of the shear strength, obtained using the proposed method for the residual flexural tensile strength, showed to be satisfactory when compared with the experimental results. A comparison among the aforementioned equations corroborate the validity of the empirical formulations proposed by Narayanan and Darwish nevertheless only the other equations provide a realistic assessments of the strength, toughness and ductility of structural elements subjected to shear loading. Over the three investigated equations, which work with the post‐cracking characterization of the material, the Italian guideline proposal is the one that, due to its wide domain of validity and the results obtained for the gathered database of beams, has been selected as the most reliable equation.
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Hall, Joanne Elizabeth. "Combined pultrude fibre reinforced plastic reinforcement and permanent formwork for concrete members." Thesis, University of Warwick, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365306.
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Jensen, Stine Maria F. "Numerical Investigation of a Post-tensioned Flat Slab with Steel Fibre Reinforcement." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for bygg, anlegg og transport, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-24262.
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This study consists of a numerical investigation of a post-tensioned flat slab without conventional longitudinal reinforcement; only steel fibres were employed to ensure sufficient ductility and shear capacity of the slab. Results were taken from a reported experiment conducted on a full scale steel-fibre reinforced flat slab (0.38 % fibre content) which was tested until failure, undergoing a ductile bending failure at a load of 6.5 kN/m2. A nonlinear finite element analysis was employed to study the experiment, including the ultimate state. A parametric study was performed using the numerical model to investigate the influence of the tensile behaviour of steel fibre-reinforced concrete (SFRC) the response of the structure. The model proved to be relatively sensitive to changes in the tensile behaviour, but the differences were not prominent until entering the nonlinear area of the load-displacement curve. A constant curve with tensile stress equal to the residual tensile strength of the SFRC provided a robust numerical model and results on the conservative side. Including a peak stress with a multilinear tensile curve provided a less stable analysis but more accurate results, however the model behaviour was stiffer than the experiment, providing too small deformations at failure. Nevertheless, the numerical model was able to display the ductile bending failure mode and moment redistribution.
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Sagnol, Loba. "Experimental and analytical study of the reinforcement of pavements by glass fibre grids." Thesis, Strasbourg, 2017. http://www.theses.fr/2017STRAD042.
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Cette thèse traite de l’effet des grilles en fibre de verre, utilisées pour renforcer les structures routières, sur la liaison entre deux couches d’enrobés bitumineux, la durée de vie en fatigue et le module de rigidité des ´éprouvettes cylindriques renforcées, ainsi que sur les déflexions mesurées sur une section de route renforcée in situ. Des essais de cisaillement (LEUTNER) ainsi que de module et de fatigue (ITT) ont été conduit sur des éprouvettes renforcées et non renforcées en utilisant différentes grilles, différentes émulsion ainsi que différentes quantités d’émulsion. Pour ces essais, une surface de test a été construite in-situ, de laquelle les ´éprouvettes ont ´été extraites. Une section de route in-situ a ´également été construite, renforcée avec 3 différentes grilles et avec deux sections de références. Les déflexions de la chaussée ont été déterminées avant et après les travaux. Une modélisation de la structure a été faites basée sur les résultats des mesures de déflexionThis PhD-study evaluates the impact of glass fibre grids, used to reinforced asphalt structures, on the bonding between two asphalt layers, the fatigue life and the stiffness modulus of reinforced cylindrical specimens as well as on the deflections measured on a reinforced in-situ road section. Shear tests (LEUTNER) as well as modulus-tests and fatigue-tests (ITT) were conducted on reinforced and unreinforced specimens, using different grids, different emulsions and different emulsion quantities. For this tests, an outdoor test-surface was constructed, from which the specimens were extracted. A in-situ road test section was also constructed, reinforced with 3 different grids and having two reference sections. The deflections of the road were determined before and after the construction works. A modelisation of the structure, based on the deflection measurements, was made
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Hariwongsanupab, Nuttapong. "Development of green natural rubber composites : Effect of nitrile rubber, fiber surface treatment and carbon black on properties of pineapple leaf fiber reinforced natural rubber composites." Thesis, Mulhouse, 2017. http://www.theses.fr/2017MULH0399/document.
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Les effets du caoutchouc nitrile (NBR), du traitement de la surface des fibres et du noir de carbone sur les propriétés des composites à base de caoutchouc naturel renforcé par des fibres d'ananas (NR / PALF) ont été étudiés. L'incorporation de NBR et le traitement de surface de la fibre ont été utilisés pour améliorer les propriétés mécaniques des composites à faible déformation, alors que le noir de carbone a été utilisé pour améliorer ces propriétés à forte déformation. La teneur en fibres a été fixée à 10 phr. Les matériaux composites ont été préparés à l'aide d'un mélangeur à cylindres et ont été réticulés sous presse permettant ainsi le maintien de l'orientation des fibres. Ces composites ont été caractérisés à l’aide du rhéomètre à matrice mobile (MDR), par analyse thermique mécanique dynamique (DMTA) et par tests de traction. La morphologie après fracture cryogénique a été observée à l'aide de la microscopie électronique à balayage (MEB). L'effet du NBR dont la teneur varie de 0 à 20 phr par rapport à la teneur totale en caoutchouc, a été également étudié. Le NBR est utilisé afin d’encapsuler totalement les fibres d’ananas (PALF) ; ceci conduisant à un meilleur transfert de contraintes entre la matrice et les fibres. La méthode de mélange a également été étudiée. Plusieurs types de silanes tels que le propylsilane, l'allylsilane et le silane-69 ont été utilisés pour traiter les fibres pré-nettoyées à l’aide d’un traitement alcalin. Les fibres silanisées ont été caractérisées par spectroscopie infrarouge à transformée de Fourier (FTIR), par spectroscopie de photoélectrons aux rayons X (XPS) et par MEB. Le traitement de la fibre par le silane-69 a permis d’augmenter fortement le module du matériau composite à faible déformation. Ce traitement a été plus efficace que l'incorporation de NBR dans les composites NR / PALF. Ceci peut s’expliquer par une possible réticulation chimique entre le caoutchouc et la fibre traitée au silane-69 plutôt qu’une simple interaction physique du NR, du NBR et de la fibre. Cependant, le renforcement par fibre réduit la déformation à la rupture. Par conséquent, du noir de carbone a également été incorporé dans les composites NR/NBR/PALF et NR/ PALF traitée, afin d’améliorer leurs propriétés ultimes. En incorporant du noir de carbone à un taux de 30 phr dans les deux composites, les propriétés mécaniques des composites ont été améliorées et peuvent être contrôlées à la fois à des déformations faibles et hautesThe effects of nitrile rubber (NBR), fiber surface treatment and carbon black on properties of pineapple leaf fiber-reinforced natural rubber composites (NR/PALF) were studied. The incorporation of NBR and surface treatment of fiber were used to improve the mechanical properties of composites at low deformation, whereas carbon black was used to improve these properties at high deformation. The fiber content was fixed at 10 phr. The composites were prepared using two-roll mill and were cured using compression moulding with keeping the fiber orientation. These composites were characterized using moving die rheometer (MDR), dynamic mechanical thermal analysis (DMTA) and tensile testing. The morphology after cryogenic fracture was observed using scanning electron microscopy (SEM). The effect of NBR from 0 to 20 phr of total rubber content was investigated. NBR is proposed to encase PALF leading to higher stress transfer between matrix and PALF. The method of mixing was also studied. For the fiber surface treatment, propylsilane, allylsilane and silane-69 were treated on the alkali-treated fiber. Treated fibers were characterized using Fourier-Transform infrared spectroscopy (FTIR), x-ray photoelectron spectroscopy (XPS) and SEM. Silane-69 treatment of fiber increased the modulus at low deformation more than the incorporation of NBR of NR/PALF composites due to the chemical crosslinking between rubber and fiber from silane-69 treatment rather than the physical interaction of NR, NBR and fiber. However, reinforcement by fiber reduced the deformation at break. Hence, carbon black was also incorporated into NR/NBR/PALF and NR/surface-treated PALF composites to improve the ultimate properties. By incorporation of carbon black 30 phr in both composites, the mechanical properties of composites were improved and can be controlled at both low and high deformations
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Ferretti, Manuel. "Non-linear mechanics of generalized continua and applications to composite materials." Thesis, Lyon, INSA, 2014. http://www.theses.fr/2014ISAL0100.
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La microstructure des matériaux constitue un outil essentiel pour optimiser les propriétés mécaniques des structures et ainsi améliorer leurs performances. Ce manuscrit est organisé comme suit : - Dans le chapitre 1 nous introduisons les aspects généraux de la mécanique des renforts fibreux.- Dans le chapitre 2 nous rappelons certains concepts fondamentaux concernant la mécanique des milieux continus classiques et les théories de deuxième gradient.- Dans le chapitre 3 nous nous proposons de présenter une première modélisation des renforts fibreux de composites en mettant en place des modèles numériques discrets. Dans un deuxième moment nous introduisons une modélisation continue de deuxième gradient et nous montrons que les termes d’ordre supérieur permettent une description satisfaisante des effets de flexion locale sur-cités.- Dans le chapitre 4 on particularise le cadre général de la mécanique des milieux continus introduit dans le chapitre 2 au cas particulier des milieux continus 2D. - Dans le chapitre 5 nous introduisons une hypothèse cinématique forte sur les déformations ad- missibles, en supposant que les mèches du renfort considéré sont inextensibles. Une méthode numérique permettant de montrer certaines solutions concernant le cas du bias extension test est codée en Mathematica et les résultats obtenus sont discutésGeneralized continuum theories may be good candidates to model micro-structured materials in a more appropriate way (both in the static and dynamic regime) since they are able to account for the description of the macroscopic manifestation of the presence of microstructure in a rather simplified way. The present manuscript is organized as follows: In chapter 1 a general description of fibrous composite reinforcements is given, with particular attention to the introduction of standard experimental tests which are used to characterize the micro- and macro-structural mechanical properties of such materials. In chapter 2 some fundamental issues concerning classical continuum mechanical models are recalled. Moreover, second gradient continuum models are introduced and discussed by means of the Principle of Virtual Work. Since the applications targeted in this manuscript are limited to static cases, we refrain here to treat the more general case including inertia effects. In chapter 3 we start analyzing some discrete and continuum models for the description of the mechanical behavior of 2D woven composites. At this stage of the manuscript, we want to show how some discrete numerical simulations allowed us to unveil some very special deformation modes related to the effect of the local bending of fibers on the overall macroscopic deformation of fibrous composite reinforcements. Such discrete simulations showed rather clearly that microscopic bending of the fibers cannot be neglected when considering the deformation of fibrous composite reinforcements. For this reason, we subsequently introduced a continuum model which is able to account for such microstructure-related effects by means of second gradient terms appearing in the strain energy density. In chapter 4 we reduce the general continuum mechanical framework introduced in Chapter 2 to the particular case of 2D continua. We put a strong accent on the geometric interpretation of second gradient deformation measures which are seen to be directly related to the in-plane curvatures of suitable coordinate lines. Such coordinate lines will be interpreted in the next chapters are the yarns of the considered 2D woven composite, so acquiring a direct physical sense. In chapter 5 we introduce a strong kinematical hypothesis on the admissible deformations, assuming that the yarns composing the woven reinforcements are inextensible. Such assumption allows us to build-up a simplified first gradient model for the behavior of 2D woven reinforcements which is still representative of their mechanical behavior. A constrained least Action principle is proposed and the associated integral Euler-Lagrange equations are presented. A numerical method allowing to show some solutions concerning the case of bias extension test is implemented in Mathematica and the obtained results are discussed
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Morphy, Ryan David. "Behaviour of fibre-reinforced polymer (FRP) stirrups as shear reinforcement for concrete structures." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0002/MQ45102.pdf.
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Grattan, S. K. T. "Development of fibre optic sensors for monitoring pH and reinforcement corrosion in concrete." Thesis, Queen's University Belfast, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.517287.
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Schley, Claus Alfred. "Reducing global performance variations of long glass fibre reinforced thermoplastics by local reinforcement." Thesis, University of Warwick, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.408237.
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Ekinci, A. "The mechanical properties of compacted clay from the Lambeth Group using fibre reinforcement." Thesis, University College London (University of London), 2016. http://discovery.ucl.ac.uk/1515980/.
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Slope failures related to pore-water dissipation, stress relaxation and desiccation cracks are major problems occurring in the UK ageing road network. The remediation works are known to cause congestion and delays that, in turn, cause financial loss and discomfort to users. Our industry partner, Mouchel, believe that it is possible to reduce the number of slope failures, maintenance costs and bring large social benefits by using soil reinforcement to reinstate failed slopes. The use of fibre reinforced soils has been a topic of research for many years, however not many applications have been seen so far. Fibres have the potential to reduce environmental impact by improving soil properties and allowing the use of local available soils. In order to increase its use, it is important to understand how the inclusion of fibres can improve soil properties, particularly in heavily overconsolidated soils, where the compacted composite has “peds” carrying properties of the intact soil. To study the soil improvement, a new compaction methodology was developed, mimicking the behaviour of the site compacted composite. Series of drained and undrained triaxial tests were performed in reinforced and unreinforced laboratory compacted samples, as well site compacted samples. In order to better understand the effect of structure, reconstituted samples were also tested. The results show that the reinforced samples, tested below a critical confining pressure, have higher strength than the unreinforced samples, whilst above this pressure the strength reduces. The data revealed that the reinforced samples appear to have a unique critical state line, whilst the unreinforced soil seems to have a transitional behaviour with a set of parallel critical state lines. The normalisation, by the intrinsic normal compression line, shows that it is possible to identify part of the state boundary surface of the compacted samples and these plot above the intrinsic state boundary surface.
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Qin, Wei. "Effect of organoclay reinforcement on pyrolytic-lignin-based carbon fibres." Thesis, University of British Columbia, 2010. http://hdl.handle.net/2429/30310.
Full textAbstract:
Pyrolytic lignin has negative effect on the quality of bio-oil in the application as fuel and energy source. On the other hand, pyrolytic lignin is also a potential alternative precursor for the manufacturing of general performance grade carbon fibre. Since clay or layered silicate reinforcement has been demonstrated to enhance the mechanical properties of many polymers, improvement of mechanical properties of carbon fibre fabricated in this work is expected. This thesis focuses on the proof-of-concept study of pyrolytic-lignin-based carbon fibres and investigates the potential of organoclay reinforcement in improving the mechanical properties of the resultant carbon fibres.
In the process of carbon fibre preparation, the pretreatment (thermal treatment under reduced pressure) was found to be a critical step in the successful preparation of carbon fibres from pyrolytic lignin. Without pretreatment, the pyrolytic lignin tended to develop hollow structures during spinning and the spun fibres fuse when thermostabilized. In the pretreatment, higher temperatures and longer time (170-180oC and 4-6 hrs) led to poor fibre spinning of pyrolytic lignin, whereas lower temperature and shorter time (150oC and 0.5-2 hrs) resulted in lignin fibres fusing in the thermostabilization process. Only a narrow window between these two extremes is suitable for carbon fibre production. By choosing the treatment condition (160°C, 30KPa for 1h) that gives the best fibre spinning, pyrolytic-lignin-based carbon fibres were fabricated, with mechanical properties and yield comparable to those based on technical lignins.
Two organoclays were employed containing modifiers with different hydrophobicity. The tensile strength of carbon fibres were improved by 12% to ~440 MPa at a 1 wt% organoclay Cloisite 30B loading. Increasing the organoclay content above 1 wt% resulted in a drop in tensile strength. The Young's modulus of pyrolytic-lignin-based carbon fibres dropped slightly upon addition of both types of organoclays (~32 GPa) and decreased as organoclay content increases. The addition of organoclay only slightly increased the overall yield of carbon fibre production from 45 wt% to 46-47%, which was independent of organoclay type and loading.
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Murray, John J. "Enhancing soil behavior through reinforcement with discontinuous recycled fiber inclusions." Thesis, Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/32766.
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Garbis, Leonidia Maria. "Lightweight concrete : investigations into the production of natural fiber reinforcement." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/82261.
Full textAbstract:
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Architecture, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 34).
The purpose of this study is to investigate the benefits of adding natural fiber tensile reinforcement to aerated concrete. Concrete is a great composite material which can be created in various proportions and with various materials to alter its strength, density and porosity, amongst other properties. Concrete which is used commonly in construction of columns, beams, and slabs acts well in compression but fails under tension. The common solution is to reinforce the structure in areas where it experiences tension with steel. There are other materials besides steel which also take tension well. Natural fibers for example come in various strengths and types and would create lighter and perhaps more sustainable beam designs. Natural fibers have been used for their availability, workability, and high tensile strengths for centuries. This research discovers how the natural fibers distribute within the mixture and how they affect the aeration of the concrete, as well as how they affect the strength. Multiple samples are cured with different fiber types and in different proportions within the mixture. Furthermore, similar experimentation is conducted to discover an ideal ratio of aggregate to aerated concrete mix. The aggregate gives the concrete greater strength and economy, but could negatively affect the aeration. The various concrete mixes are poured and allowed to cure to maximum strength before indirect tensile tests and compression tests are conducted. The effects of creating smooth aerated concrete molds are also investigated. All experiments conducted are precursory to an ultimate tensile reinforced aerated concrete beam design with an aggregate mix and smooth surfaces.
by Leonidia Maria Garbis.
S.B.
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Wang, J., S. Dong, Ashraf F. Ashour, X. Wang, and B. Han. "Dynamic mechanical properties of cementitious composites with carbon nanotubes." Elsevier, 2019. http://hdl.handle.net/10454/17465.
Full textAbstract:
YesThis paper studied the effect of different types of multi-walled carbon nanotubes (MWCNTs) on the dynamic mechanical properties of cementitious composites. Impact compression test was conducted on various specimens to obtain the dynamic stress-strain curves and dynamic compressive strength as well as deformation of cementitious composites. The dynamic impact toughness and impact dissipation energy were, then, estimated. Furthermore, the microscopic morphology of cementitious composites was identified by using the scanning electron microscope to show the reinforcing mechanisms of MWCNTs on cementitious composites. Experimental results show that all types of MWCNTs can increase the dynamic compressive strength and ultimate strain of the composite, but the dynamic peak strain of the composite presents deviations with the MWCNT incorporation. The composite with thick-short MWCNTs has a 100.8% increase in the impact toughness, and the composite with thin-long MWCNTs presents an increased dissipation energy up to 93.8%. MWCNTs with special structure or coating treatment have higher reinforcing effect to strength of the composite against untreated MWCNTs. The modifying mechanisms of MWCNTs on cementitious composite are mainly attributed to their nucleation and bridging effects, which prevent the micro-crack generation and delay the macro-crack propagation through increasing the energy consumption.
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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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Cao, Qian. "Development of pseudo-ductile permanent formwork with glass fiber reinforced plastics reinforcements /." View abstract or full-text, 2007. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202007%20CAO.
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Stig, Fredrik. "An Introduction to the Mechanics of 3D-Woven Fibre Reinforced Composites." Licentiate thesis, Stockholm : Skolan för teknikvetenskap, Kungliga Tekniska högskolan, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-10235.
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Worner, Victoria Jane. "Use of Glass Fibre Reinforced Polymer (GFRP) reinforcing bars for concrete bridge decks." Thesis, University of Canterbury. Civil & Natural Resources, 2015. http://hdl.handle.net/10092/10724.
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Glass Fibre Reinforced Polymer (GFRP) bars have been developed as an alternative to steel reinforcement for various structural concrete applications. Due to their non-corrossive nature, they are particularly suited for harsh environments where steel reinforcement is prone to corrosion. The purpose of this research is to determine the feasibility of GFRP reinforcing bars as concrete bridge deck reinforcement for locations, such as coastal New Zealand, where the non-corrosive benefits of GFRP may offer an alternative to traditional mild steel reinforcement. GFRP use as structural reinforcement may offer life-cycle cost benefits for certain structures as maintenance to repair corroded reinforcement is not necessary. The use of GFRP reinforcement in a New Zealand design context was investigated to directly compare the structural performance of this alternative reinforcing product. Mateen-bar, manufactured by Pultron Composites Ltd, is the GFRP reinforcing bar used in the experimental tests.
Experimental investigation of tensile properties of GFRP bar samples was carried out to understand the mechanical behaviour of GFRP reinforcement and validate the manufacturer’s specifications. This series of tests highlighted the complexities of carrying out tensile testing of FRP products, due to the inability to grip the GFRP directly in a testing machine without crushing the specimen.
Two phases of full-scale tests were carried out to compare the performance of bridge deck slabs reinforced with typical mild steel and GFRP reinforcing bar. This experimental testing was different to most existing research on GFRP reinforced slab performance as it did not compare the performance of a GFRP reinforcing bar area equivalent to steel, but was designed in such a way as to dependably give the same moment capacity of the steel reinforced slab design. This incorporated the recommended limit of 20% of design stress given by the manufacturer which led to an apparent over-reinforced section for the GFRP slab design. The aim of the experiments was to investigate the comparative performance of a typical New Zealand bridge deck design and a GFRP reinforced equivalent designed in such a way as is currently recommended by the manufacturer. The over-reinforcement lead to differences in conclusions drawn by other authors who have studied GFRP reinforced slab behaviour.
Both flexural and concentrated loading (simulating vehicle loading) tests were carried out on both the steel and GFRP reinforced slab designs. Due to over-reinforcement the GFRP slab was considerably stiffer and stronger than the steel design, indicating that serviceability issues are unlikely to be as much of a design issue as existing literature would suggest. Deflection prediction models generally underestimate the strength of over-reinforced sections. All slabs failed in punching shear under concentrated loads, indicating that punching shear may be a critical failure mechanism for GFRP reinforced slabs
Based on the findings from the extensive experimental phases, a set of design recommendations were made to further improve the potential for GFRP to be used for bridge deck design in a New Zealand context.
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Davenport, Rebecca A. "An investigation into the manufacture and mechanical properties of an Al-steel hybrid MMC." Thesis, Brunel University, 2018. http://bura.brunel.ac.uk/handle/2438/17033.
Full textAbstract:
One of the most significant challenges in the composite development field is to find a low-cost manufacturing route capable of producing large volumes of material. This thesis develops and characterises a potential avenue for addressing this, an induction furnace-based process. This process produced a composite of A357 matrix and 10% wt Dramix 3D 80/30 SL steel fibres. The method was evaluated by microstructural analysis and optimum casting parameters were approximated. The fibres were introduced to liquid A357 at 700°C and the composite was brought to a measured temperature of 650°C over not more than 120 seconds before being removed from the furnace and cooled. 10% wt was the ideal reinforcement ratio for this process. Characterising the tensile and compressive strength of the composite material, it reached a peak stress 130% higher than A357 produced under the same conditions, though the peak stresses were still 20% of the literature values for T6 tempered A357. This suggests the need for development of a temper which does not degrade the properties of the composite. 3-point bending tests and some tensile specimens also showed post-failure strength. Under dynamic loading, the composite showed a peak stress in excess of 100 MPa without reaching maximum compression under SHPB loading, and comparable performance to SiC-reinforced MMCs under ballistic testing. The linear decrease in work-hardening with increasing distance from the impact site shows shock and pressure-pulse dissipation properties, attributed to the difference in acoustic impedance between the matrix and the reinforcement.