Réalisé dans le cadrr du pôle de compétitivité Véhicule du Futur » de la région ,11k.c Franche Comté_ cc uas_ul de thèse porta sur la hmblcmatsque du remplacement des étoffes complexes textiles utilisées dans les applications d'habillage intérieur automobile. La législation sur les véhicules hors d'usage impose des produits automobiles a 1 $ "), rccyclablcs et t 95' réutilisables dl ici janvier 2015. Alin de rebondie u la problématique posée ainsi qua la législation Europécnnc, des industriels et des acteurs de la recherche de la regain mulhousienne ont lias aillé ensemble dans le cadre du poilez VERTILAP" sur le développement d'un nouveau textile non-tissé 3D. Ce travail de thèse a eu pour objectif de développer le proucde de ! abris ation de ces nouveaux matériaux ainsi que les produits non-tisses 3D obtenus. La démarche de développements procédé produits a consisté Ii faire évoluer le prototype expérimental VERTILAP' au travers de la caractérisation physique et mécanique en compression des produits obtenus. Des méthodes ci dcsj outils de caractérisations adaptés a ces nouveaux produits ont etc mis au point. L'analyse de résultats obtenus s'est appuyée sur les outils statistiques i abn de valider ces résultats. Une étude comparative avec les produits contenant de la mousse polyuréthane (PU) a permis de montrer que ces nouveaux non-tissés 3D pouvaient être utilisés en remplacement des mousses PU. La réalisation de prototypes pour des applications d'habitacle autinnobilu a été faite et a prouvé la faisabilité industrielle d'un tel remplacement. Les résultats de ce travail ont été utilisés pour [élaboration du cahier des charges d'ur prototype semi industriel VERTILAP". / The question of the recycling of the laminated textile fabrics especially in the automotive indusuy represents one of the main requests and challenge of the car manufactures and the OEM's sine 2000. indced, it is nowadays impérative l'or car industry to promote ecological methods of developinent in regard to new consumer sensibility. Rcgarding the Europcan directives 2000 CE53, the automotive products should be at 85% recyclable and at 95% reusable by January 2015. In order to answer this issue, sonie textile industrialists and researchers are working together, through the VERTILAP projet to develop a new material as a 3D nonwoven which will be used to substitute polyuréthane (PU) foam. This work aims to develop the VERTILAP experimental prototype through the physical and mechanical characterizations in compression of thosc new 3D nonwovens. Methods and tools have been canied out to reach Chat goal. Statistical analyses have been used to validate the obtained experimental data. A comparative study between the VERTILAP" products, issued from the VERTILAP" process, and the automotive PU foams bas shows that the new 3D nonwovens can be used to substitute the PU foams. VERTILAP" experimental prototypes such as headrest upholstery and door panel have been developed and have proved the feasibility of the foam exchange. The already obtained results of this work have been taking alto accourt in the spécifications of the new VERTILAP" serai industrial prototype.

The purpose of this study was to investigate the effects of mold temperature, initial resin temperature, and the vacuum, applied at resin exit ports, on the mechanical properties of epoxy matrix woven glasss fiber reinforced composite specimens produced by Resin Transfer Molding (RTM). For this purpose, six different mold temperatures (25&ordm / , 40&ordm / , 60&ordm / , 80&ordm / , 100&ordm / , and 120&ordm / C), two initial resin temperatures (15&ordm / and 28&ordm / C), and vacuum (0.03 bar) and without vacuum (~1 bar) conditions were used. Specimens were characterized by using ultrasonic (C-Scan) inspection, mechanical tests (Tensile, Flexural, Impact), thermal analyses (Ignition Loss, TGA) and scanning electron microscopy (SEM). It was generally observed that mechanical properties of the specimens produced with a mold temperature of 60&ordm / C were the best (e.g. 16%, 43%, and 26% higher tensile strength, Charpy impact toughness and flexural strength values, respectively). When vacuum was not applied, the percentage of &ldquo / voids&rdquo / increased leading to a decrease in mechanical properties such as 26% in Charpy impact toughness and 5% in tensile and flexural strength. Lower initial resin temperature also decreased mechanical properties (e.g. 14% in tensile strenght and 18% in Charpy impact toughness).

In this study structural design, analysis and composite manufacturing applications for a tactical UAV, which was designed and manufactured in Aerospace Engineering Department of Middle East Technical University (METU), is introduced. In order to make an accurate structural analysis, the material and loading is modeled properly. Computational fluid dynamics (CFD) was used to determine the 3D pressure distribution around the wing and then the nodal forces were exported into the finite element program by means of interpolation from CFD mesh to finite element mesh. Composite materials which are mainly used in METU TUAV are woven fabrics which are wetted with epoxy resin during manufacturing. In order to find the elastic constants of the woven fabric composites, a FORTRAN code is written which utilizes point-wise lamination theory. After the aerodynamic load calculation and material characterization steps, linear static and dynamic analysis of the METU TUAV&rsquo / s wing is performed and approximate torsional divergence speed is calculated based on a simplified approach. Lastly, co-cured composite manufacturing of a multi-cell box structure is explained and a co-cured multi-cell box beam is manufactured.

Textile composites can be tailored to meet specific thermo-mechanical requirements for structural applications. The focus of this research is on 2x2 biaxial braided composites since they have good stiffness and strength properties. Moreover, they have potentially better impact and fatigue resistance than laminated composites. Along with good properties, they have a reduced manufacturing cost because much of the fabrication can be automated. In order to exploit these benefits, thorough understanding of the effect of various factors on their material behavior is necessary. Obtaining effective mechanical properties is the first order of concern in any structural analysis. This work presents an investigation of the effect of various parameters like braid angle, waviness ratio, stacking sequence and material properties on the effective engineering properties of the 2x2 braids. To achieve this goal, three dimensional finite element micromechanics models were developed first. Extensive parametric studies were conducted for two material systems: 1). Glass (S2) fiber / epoxy (SC-15) matrix and 2). Carbon (AS4) fiber / Vinyl Ester (411-350) matrix. Equivalent laminated materials with angle plies and a resin layer were also analyzed to compare the difference in predictions from the full three dimensional finite element analysis of the 2x2 braided composites. A full three-dimensional stress state exists in braids even for very simple loading. In order to locate the potential damage spots, the stress distributions in both the matrix and the tows were predicted. The effect of braid angle on location and magnitude of peak stresses was determined.

Current military-grade rifle body armor technology uses hard ballistic plates positioned on top of flexible materials, such as woven Kevlar® to stop projectiles and absorb the energy of the impact. However, absorbing the impact energy and stopping a rifle projectile comes at a cost to the wearer - mobility. In this thesis, a new concept for personal body armor is proposed - a semi-flexible hybrid body armor. This hybrid armor is comprised of two components that work as a system to effectively balance the flexibility offered by a soft fabric based armor with the protection level of hard plated armor. This work demonstrates techniques used to analyze and design the hybrid armor to be compliant with National Institute of Justice guidelines. In doing so, finite element analysis is used to simulate the effect of a projectile impacting the armor at various locations, angles, and velocities, while design of experiments is used to study the effect of these various impact combinations on the ability of the armor component(s) (including the wearer) to absorb energy. The flexibility and protection offered by the two component armor system is achieved by the use of proven technique and innovative geometry. For the analytical design, the material properties, contact area(s), dwell duration, and energy absorption are all carefully considered. This yields a lightweight but yet effective armor, which is estimated to weigh 36% less than the current military grade hard body armor. Using ANSYS, several simulations were conducted using finite element analysis, including a direct center impact, along with various other impacts to investigate possible weak points in the armor. In doing so, it is determined that only one of these impact locations is indeed a potential weak point. The finite element analysis continues to show that a rifle projectile impacting at an oblique angle reduces the energy transferred to the wearer by about 25% (compared to a direct impact). A design of experiments approach was used to determine the influence of various input parameters, such as projectile impact velocity and impact location. It is shown that the projectile impact velocity contributes 36% to the ability of the wearer to absorb energy, whereas impact velocity contributes only 13% to the energy absorbed by the top armor component. Furthermore, the analysis shows that the impact location is a highly influential factor (with a 69% contribution) in the energy absorption by the top armor component.

High precision inflatable surfaces were introduced when NASA created the ECHO 1 Balloon in 1960. The experiment proved that inflatable structures were a feasible alternative to their rigid counterparts for high precision applications. Today inflatable structures are being used in aviation and aerospace applications and the benefits of using such structures are being recognized. Inflatable structures used in high precision structures require the inflatable surfaces to have controllable and predictable geometries. Many applications such as solar sails and radar reflectors require the surface of such structures to have a uniform surfaces as such surfaces improve the efficiency of the structure. In the study presented, tests were conducted to determine which combination of factors affect surface flatness on a triangular test article. Factors tested include, three boundary conditions, two force loadings, and two fabric orientations. In total, twelve tests were conducted and results showed that which force loading and fabric orientations used greatly affected the Root Mean Square (RMS) of the surface. It was determined that using the triangular clamp along with 00 fabric orientation and high force loading provided the best results.

Thesis (M.S.)--Michigan State University. Dept. of Mechanical Engineering, 2008. / Title from PDF t.p. (viewed on July 29, 2009) Includes bibliographical references (p. 108-110). Also issued in print.

Thesis (M.S.M.E.)--University of Delaware, 2006. / Principal faculty advisor: Suresh G. Advani, Dept. of Mechanical Engineering. Includes bibliographical references.

Pour optimiser les structures des aéronefs, il est maintenant nécessaire de concevoir le matériau au « juste-besoin », de façon à diminuer le ratio masse/performances. Par une bonne gestion du procédé de fabrication et un choix judicieux des matériaux constitutifs, les composites à renfort tissé et à matrice organique ont ce potentiel. Mais pour l’exploiter pleinement, de nouvelles approches adaptées à ce type de matériau doivent être développées. Pour cela, une chaîne de calcul multimodèle est proposée, permettant de prévoir les propriétés mécaniques élastiques saines ou endommagées du matériau à partir de ses paramètres de conception. Cette chaîne est établie à l’échelle mésoscopique, pour pouvoir prendre en compte la géométrie du renfort. Une procédure spéciale de création de maillages de cellules mésoscopiques de composites tissés a été développée, de façon à faire le lien entre la déformée du renfort après mise en forme, obtenue par simulation EF, et les autres modèles de la chaîne (injection de résine, cuisson du composite, comportement mécanique). Le bon fonctionnement de l’approche est montré par l’étude de deux cas-tests, un renfort de quatre plis de taffetas et un renfort de quatre plis de satin de 5, chacun compactés à différents niveaux et selon plusieurs configurations d’imbrication de plis. Enfin, pour anticiper la validation de la chaîne de modélisation, une étude expérimentale comparative entre plusieurs composites tissés compactés à différentes épaisseurs a été menée. Ce travail se place dans le cadre de la construction future d’une chaîne multiéchelle plus globale qui, parcourue dans le sens inverse, permettra de concevoir le matériau sur-mesure en fonction des performances structurales locales désirées. / In order to optimize aeronautic structures, the manufacturing process must be tailored to the structural needs, with the aim of reducing the density/performance ratio. Polymer composites with woven reinforcements offer a large flexibility due to a vast choice of constituent materials and manufacturing process parameters. However, to entirely exploit their potential, new design methods specifically adapted to this type of material have to be developed. For this purpose, a modeling chain is proposed, which is able to predict the elastic properties of the intact or damaged material, by incorporating the manufacturing process parameters. The chain is built at the mesoscopic scale, to take into account the reinforcement geometry. A special procedure to generate finite element (FE) meshes of mesoscopic representative unit cells of woven composites has been developed, which links the deformation of the reinforcement, obtained from FE calculations, to the other models of the chain (resin injection, curing, and mechanical behavior). Two materials are studied to show the potential of the modeling chain: A four ply lay-up of a plain weave and of a satin weave fabric are considered, each of them having several compaction ratios and different nesting between the plies. With the aim of a validation of the modeling chain, multi-instrumented experimental tests have been carried out on several multi-layer plain weave composites with different thicknesses. In future applications, the proposed strategy will be placed in a toolbox able to design optimum woven composite structures based on local performance requirements.

In recent years, the use of textile composites has grown rapidly primarily due to the high strength-to-weight ratio which they offer. The applications of fibre reinforced composites include a range of industries including aerospace, automotive, marine, civil construction, wind energy and sports. The textile reinforcements used for composites include woven, knitted, braided and stitch-bonded preforms. Among these, woven fabrics are the most widely used reinforcements which comprise interlaced warp and weft yarns oriented at 0o and 90o, respectively. This research concerns woven fabrics wherein the interlacing sets of yarns are oriented at bias. The main focus is the development of manufacturing concepts for bias woven preforms. Following a thorough study on existing bias technologies, five bias weaving concepts have been proposed for making bias woven preforms. With regard to the first of these concepts, a Desktop Bias Weaving (DBW) machine has been developed. A range of elementary and compound bias woven preforms have been successfully produced using the DBW machine. The preforms have been consolidated using the vacuum resin infusion process to make textile composites. The mechanical properties of the composite materials have been assessed, and their structure has been analysed to observe tow geometry using advanced imaging techniques such as X-ray tomography. The next step has been the development of advanced Bi-axial Bias (BiB) weaving concepts for producing quasi-isotropic bias woven preforms. Here both sets of interlacing yarns are oriented at bias. Such fabric formation requires a double rapier weft insertion mechanism. With regard to this, four concepts have been proposed and two BiB weaving machines have been developed accordingly. BiB woven preforms based on fundamental plain, twill and satin weaves have been fabricated successfully and impregnated with epoxy resin to make laminates. The weave geometry in the composite samples has been analysed using Scanning Electron Microscopy.