This thesis describes the manufacturing, structural analysis and testing of a composite cylinder for space application. This work includes the design and fabrication of a reusable multicomponent mandrel made of aluminum and steel and the manufacturing of a carbon fiber reinforced tube in an epoxy resin matrix. This structure intends to serve as the optical lens housing onboard a spacecraft. In addition, some future work needs to be done before this component is certified. The objective is to determine if the composite meets the stiffness and strength requirements for lens housing. The structural analysis is made by means of a finite element model simulating the true boundary conditions. The testing includes the design of a fixture to allow the composite cylinder to be mounted in one the testing machines at the Department of Aerospace Engineering at Texas A&M University and the preparation for the actual test. The response to the experimental analysis will be compared to the numerical simulation to verify the results.

This thesis describes the manufacturing, structural analysis and testing of a composite cylinder for space application. This work includes the design and fabrication of a reusable multicomponent mandrel made of aluminum and steel and the manufacturing of a carbon fiber reinforced tube in an epoxy resin matrix. This structure intends to serve as the optical lens housing onboard a spacecraft. In addition, some future work needs to be done before this component is certified. The objective is to determine if the composite meets the stiffness and strength requirements for lens housing. The structural analysis is made by means of a finite element model simulating the true boundary conditions. The testing includes the design of a fixture to allow the composite cylinder to be mounted in one the testing machines at the Department of Aerospace Engineering at Texas A&M University and the preparation for the actual test. The response to the experimental analysis will be compared to the numerical simulation to verify the results.

Natural fiber-reinforced composites are now finding extensive uses in various fields from household articles to automobiles. These composites can score high compared to common synthetic fiber-based composites, notably glass fiber-reinforced composites, in areas such as occupational safety and health, and impact on environment. The current research work is motivated by the need for exploring jute fibers as replacement for glass fibers for various engineering design applications including more demanding impact protection applications as in automotive body structures. In the current work, detailed mechanical characterization of jute-polyester (JP) composite laminates till failure has been carried out for tensile, compressive and flexural loads by varying volume fraction of jute fibers. The effect of fiber volume fraction on mechanical properties is shown. Because of the potency of closed thin-walled components as structural energy-absorbers, a comprehensive experimental study has been performed, for the first time, comparing the behaviors of various geometric sections of JP and glass-polyester (GP) composite tubes under axial quasi-static and low velocity impact loading. Additionally, for jute-reinforced plastic panels to be feasible solutions for applications such as automotive interior trim panels, laminates made of such materials should have adequate perforation resistance. Thus, a detailed comparative study has been carried out for assessing the performance of JP laminates vis-a-vis GP plates under low velocity impact perforation conditions. As high-end product design is heavily driven by CAE (Computer-Aided Engineering), the current research work has also focused on the challenging task of developing reliable modeling procedures for explicit finite element analysis using LS-DYNA for predicting load-displacement responses and failures of JP composites under quasi-static and impact loading conditions. In order to extend the applications of JP composites to structurally demanding applications, hybrid laminates made of jute-steel composites and jute with nanoclay-reinforced polyester have been investigated and the considerable enhancement of mechanical properties due to hybridization is shown. Furthermore, a comprehensive study has been conducted on the behavior of JP laminates for varying degrees of moisture content until saturation, and the efficacy of hybrid laminates in this context has been shown.

Dans l’optique de la conception et du développement d’un siège aéronautique et afin derespecter la règlementation sécuritaire en vigueur, la structure du siège développé doitpermettre une dissipation rapide de l’énergie perçue en cas de crash aérien (Fig. 1), ceci dansle but de protéger les passagers. La majorité des systèmes intégrés à la structure des sièges etpermettant cette absorption d’énergie (Fig. 2) est constituée de composants métalliques qui sedéforment plastiquement pour dissiper l’énergie due au crash. Actuellement, l’industrie et larecherche se tournent vers les matériaux composites pour substituer de tels systèmes.Cependant le comportement de ces matériaux lors de sollicitations mécaniques sévères estfortement différent des matériaux métalliques, notamment dû au fait que les mécanismesd’endommagement sont très distincts.Le but de cette étude portant sur des structures tubulaires composites est d’évaluer leurcapacité à dissiper l’énergie. A cette fin, différentes stratifications ont été testées encompression (Fig. 3 et 4) dans le but de déterminer leur comportement, comparer leurspropriétés et calculer leurs valeurs de SEA (absorption d'énergie spécifique, en kJ.kg-1)servant à évaluer leur aptitude à dissiper l’énergie engendrée en cas de crash. Ces dernièressont issues des courbes effort-déplacement obtenues lors des essais d’écrasement (Fig. 5). Lesdifférents essais de compression ont été instrumentés et suivis au moyen de caméras rapides etdes images post-essais ont été réalisées par tomographie pour comprendre les mécanismesd’endommagement mis en jeu (Fig. 4 et 6). Ces essais ont été réalisés à vitesse de chargementquasi-statique puis dynamique et selon diverses conditions limites. Les différents résultats decomportement en compression sont également utilisés dans le but de construire et enrichir unmodèle de calcul par éléments finis (Fig. 7 et 8) permettant de simuler la réponse de structurescomposites de différentes natures soumises au crash en intégrant la géométrie et lacomposition de la structure (Fig. 8).L’objectif de ce travail de recherche est ainsi d’évaluer l’énergie pouvant être dissipée par desstructures tubulaires composites, de comparer les absorptions induites par des structurescomposites de compositions différentes, et/ou bi-matériaux, et enfin de fournir un modèleéléments finis représentant le comportement de structures composites en compression jusqu’àl’endommagement et la ruine de la structure.Il a ainsi été établi qu’en chargement statique, un stratifié unidirectionnel orienté à 0° etstabilisé par des plis de tissus répond fortement aux attentes en terme de dissipation d’énergie,mais pas en sollicitation dynamique. Dans ce cas, une stratification à 90° semble plusadéquate. D’autre part, un confinement forcé vers l’intérieur est avantageux dans la plupartdes cas, réduisant le pic d’effort initial sans diminuer drastiquement la valeur de SEA. / With the perspective of the design and development of an aircraft seat and in order to respectthe safety regulations in effect, the structure of the developed seat must allow for a swiftdissipation of the energy received in the event of an aircraft crash (Fig. 1) so as to protect thepassengers. The majority of systems integrated into the seats structure and allowing energydissipation (Fig. 2) consists of metal components that sustain plastic deformation to dissipatethe energy induced by the crash. Currently, industry and research sectors are turning theirfocus towards composite materials to substitute such systems. However, the behavior of thesematerials during severe mechanical stress is strongly different from metallic materials, inparticular due to the fact that damage mechanisms are very distinct.The purpose of this study on composite tubular structures is to evaluate their ability todissipate the energy. To this end, different laminate structures were tested in compression(Fig. 3 and 4) in order to identify their behavior, compare their properties and calculate theirSEA value (Specific Energy Absorption, in kJ.kg-1) used to evaluate their capacity to dissipatethe energy generated during a crash. Those are resulting from the load-displacement curvesobtained during the crushing tests (Fig. 5). The various compression tests were instrumentedand monitored by means of rapid imaging cameras and post-crushing tomographic imaginghas been realized in order to understand the damage mechanisms involved (Fig. 4 and 6).Testing has been carried out under quasi-static and dynamic loading and using severalboundary conditions. The different results of compression and crushing behavior are also usedin order to build and improve a finite element calculation model (Fig. 7 and 8) allowing tosimulate the response of composite structures of different natures subjected to crash byintegrating the geometry and the composition of the structure (Fig. 8).The objective of this research work is thus to evaluate the energy that can be dissipated bycomposite tubular structures, to compare the absorption values induced by compositestructures of different compositions, and/or bi-materials, and, finally, to provide a finiteelement model representing the behavior of composite structure submitted to compressionuntil damage and fracture of the structure.It has consequently been established that in static loading, a unidirectional laminate orientedat 0° and stabilized by woven plies strongly meets the expectations in terms of energydissipation, but that is not the case in dynamic loading. In this case, a 90° stratification seemsmore adequate. Incidentally, an inner constrained containment is more effective in most cases,reducing the initial peak load without drastically reducing the SEA value.