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Ce travail traite la problématique des bulles d’air contenues dans les pièces composites mises en œuvre par le procédé RTM. La modélisation des phénomènes de création, de compression et de transport de ce type de défauts est présentée. Notamment l’adoption d’un nouveau modèle de création des bulles d’air, de transport, et l’estimation des porosités à double échelle de pores ainsi que la saturation finale de la préforme sont données. / This work covers the problematic of air bubbles entrapped during manufacturing composite parts via the RTM process. Modeling creation, compression, and transport of this type of defaults is presented here. Likewise, a new approach of air bubble’s creation, transport modeling, simulation of porosities at dual scale of pores, and estimation of the final saturation of the preform are given.

The aim of this study is to investigate and compare the properties of two layer carbon epoxy composite plates manufactured using various resin impregnation techniques / Resin Transfer Molding (RTM), Light RTM (LRTM), Vacuum Assisted RTM (VARTM) and Vacuum Packaging (VP). Throughout the study a different packaging method was developed and named Modified Vacuum Packaging (BP). The mechanical properties of composite plates manufactured are examined by tensile tests, compressive tests, in-plane shear tests and their thermal properties are examined by Differential Scanning Calorimetry (DSC) and Thermo Gravimetric Analysis (TGA) tests. All tests were performed according to suitable ASTM standards. The performance of specimens from each process was observed to vary according to the investigated property / however the VP process showed the highest performance for most properties. For most of the tests, VARTM, LRTM and RTM methods were following VP process in terms of performance, having close results with each other.

Compression Resin Transfer Molding (CRTM) is an advanced liquid molding process for producing continuous fiber-reinforced composite parts in relatively large dimensions and with high fiber volume fractions. This thesis investigates this process for the purpose of producing continuous fiber reinforced composites with particle fillers. In many composites, fillers are used within the resin for various reasons such as cost reduction and improvement of properties. However, the presence of fillers in a process involving resin impregnation through a fibrous medium can result in a composite with non-homogeneous microstructure and properties. This work aims to model the resin impregnation and particle filtration during injection and compression stages of the process. For this purpose, a previously developed particle filtration model is adapted to CRTM. An appropriate commercial software tool is used for numerical solution after a survey of available packages. The process is analyzed based on the developed model for various process scenarios. The results of this study aim to enhance the understanding of particle-filled resin impregnation and particle filtration phenomena in the CRTM process and are likely to be used towards designing optimum process configurations for a desired outcome in the future.

L’intégration des contraintes d’industrialisation, des pièces en matériaux composites, en conception préliminaire, est un enjeu majeur de la compétitivité des entreprises, et s’inscrit dans une démarche de développement durable. Un travail de captation et de mise en forme de la connaissance industrielle a permis de développer une stratégie d’optimisation. Cette stratégie repose sur une approche multi-métiers, elle permet d’estimer la performance technique et économique d’une solution d’industrialisation. L’estimation de la performance est basée sur l’évaluation, pour chaque solution d’industrialisation, du risque de rupture du composant assemblé, du niveau d’intégration fonctionnelle et du coût de fabrication. La définition de la meilleure alternative est obtenue par la comparaison de la performance de solutions et s’appuie sur des méthodes et outils d’aide à la décision. Le risque de rupture est estimé à partir des écarts entre des caractéristiques de la pièce fabriquée par procédé Resin Transfer Molding (RTM) et les caractéristiques nominales. Les caractéristiques de la pièce fabriquée prises en compte sont : - les écarts géométriques, - les écarts de caractéristiques mécaniques. Dans l’industrie aéronautique, certaines pièces de structure en matériaux composites sont réalisées par le procédé RTM. Dans ce type de mise en forme, les caractéristiques mécaniques du composant sont directement liées au niveau d’imprégnation de la préforme. Dans le travail de thèse, les défauts d’imprégnation sont identifiés comme des écarts volumiques d’imprégnation. Ces écarts ont pour conséquence d’altérer les propriétés mécaniques du matériau qui constitue la pièce. L’estimation des écarts volumiques d’imprégnation est obtenue à partir de l’analyse des résultats de la simulation par éléments finis de l’écoulement de résine dans le renfort fibreux (logiciel Pam RTM®). La géométrie de la pièce obtenue par procédé RTM diffère de la géométrie nominale, cet écart est due en partie aux différences entre les caractéristiques physiques des constituants du matériau composite. Les variations géométriques de la pièce fabriquée sont identifiées comme des écarts géométriques de fabrication. Les écarts géométriques sont compensés, lors de la phase d’assemblage, par des déformations garantissant les contacts avec les pièces adjacentes. Ces déformations génèrent un état de contraintes mécaniques au sein de la pièce. La quantification de l’état de contraintes mécaniques est obtenue à partir d’une simulation thermomécanique par éléments finis réalisée par le logiciel Samcef®. L’aide à la décision est basée sur l’étude combinée de l’état de contraintes mécaniques due à la compensation des écarts géométriques et de l’incidence des écarts volumiques d’imprégnation sur les propriétés mécaniques de la pièce. Trois critères permettent d’estimer le risque de rupture du composant assemblé : un critère de rupture des matériaux composites quantifie le risque de rupture, les deux autres critères, prenant en compte les défauts d’imprégnation, majorent le risque de rupture. Afin de faciliter l’interprétation des résultats et la phase de comparaison de solutions, le risque de rupture est présenté sous forme d’une cartographie. En fonction des couplages des valeurs des critères, une optimisation de la conception et/ou de l’industrialisation est proposée. Une évaluation du niveau d’intégration fonctionnelle ainsi que du coût de fabrication complète la démarche d’aide à la décision. / Integrating industrialization constraints of composite materials into preliminary design is a major challenge for companies in terms of competitiveness, and is part of a sustainable development approach. Work on capturing and formatting industry knowledge has helped develop a design optimization strategy. This strategy is based on multidisciplinary rules, and estimates the technical and economic performance of an industrialization solution. This estimate is based on the evaluation of failure risk of component assembly, level of functional integration and manufacturing cost. The definition of the best alternative is obtained by comparing solution performances, relying on decision support methods and tools. The failure risk is estimated from differences between the characteristics of the part manufactured by Resin Transfer Molding Process (RTM) and the nominal part (CAD). The following characteristics of the manufactured part are taken into account: ? - geometric deviations, ? - characteristic mechanical deviations. In the aviation industry, some structural composite parts are manufacture by RTM. In this type of manufacture, the mechanical properties of the component are directly related to the level of preform impregnation. In this thesis, the impregnation defects are identified as volumic impregnation deviations. These deviations have the effect of altering the mechanical properties of material. Estimated volume impregnation deviations are obtained by analysing the results of the finite element simulation of resin flow into the fibrous reinforcement (software Pam RTM ®). The part geometry obtained using the RTM process differs from the nominal geometry, with the deviation due partly to differences between the physical components of the composite material. The geometric variations in the manufactured part are identified as geometric manufacturing deviations. These geometric deviations are offset, in the assembly phase, by deformations due to contact with adjacent parts, which generate a state of mechanical stress within the part. The mechanical stress state is quantified from a finite element thermomechanical simulation carried out using the Samcef ® software. Decision support is based on the combined study of the state of mechanical stress due to the compensation of geometric deviations and the incidence of volume impregnation deviations on the mechanical properties of the part. Three criteria are used to estimate the failure risk of the assembled component: a composite materials failure criterion quantifies failure risk; the other two criteria, taking into account the impregnation defects, increase the failure risk. To facilitate interpretation of results and the solution comparison phase, the failure risk is represented by mapping. Depending on the coupling values of the criteria, optimizing the design and/or industrialization is proposed. An evaluation of the level of functional integration and manufacturing cost complete the decision support process.

Bismaleimide resins are important in aerospace applications as matrix component of composite materials due to their high thermal and mechanical properties. 4,4&rsquo / -bismaleimidodiphenylmethane (BMI) which is the most widely used bismaleimide, was synthesized starting from maleic anhydride and 4,4&rsquo / -diaminodiphenylmethane (MDA). N,N&rsquo / -diallylaminodiphenyl methane (ADM), N,N&rsquo / -diallylaminodiphenyl sulfone (ADS) and N,N&rsquo / -diallyl p-phenyl diamine (PDA) were synthesized by allylating primary aromatic diamines. Nine different prepolymers with 1:1, 1.5:1 and 2:1 molar ratios of BMI/diallyl compound were prepared and cured. The effect of increase in BMI ratio on thermal properties of the resin systems were investigated via Differential Scanning Calorimetry (DSC) and Thermal Gravimetric Analyzer (TGA). DSC results showed that the curing temperature of the resins increased due to the increase in BMI ratio in the resins. Thermal gravimetric analysis showed that incorporation of BMI monomer improved the thermal stability of the resins. BMI/ADM resin system showed better thermal stability compared to BMI/ADS and BMI/PDA resins. Processing characteristics of resins having 1:1 and 1.5:1 mole ratio of BMI/ADM were investigated by viscosity measurements and these resins were found to be suitable for composite production with Resin Transfer Molding (RTM). Composites were manufactured by RTM technique using two different mole ratios of BMI/ADM resins as matrix component. The effect of different matrix composition on thermal and mechanical properties of the composites were investigated. The concept of this thesis work was arised from the requirements of some projects carried out in T&uuml / bitak-SAGE. Keywords: Bismaleimide resins, composite, thermal properties, resin transfer molding.

Composite materials have the potential to revolutionize life in the 21st century. They are contributing significantly to developments in aerospace, hydrogen fuel cells, electronics and space exploration today. While a number of composite material processing methods exist, resin transfer molding (RTM) has the potential of becoming the dominant low-cost process for the fabrication of large, high-performance products. RTM has many advantages over alternative processes, including the capability of producing complex 3D shapes with a good surface finish, the incorporation of cores and inserts, a tight control over fiber placement and resin volume fraction and the possibility of embedding sensors into manufactured components for structural health monitoring. Part of the reason RTM has not received widespread use is due to its drawbacks such as its relatively trial and error nature, race tracking, washout, high cycle time and void formation. The basic operation of the process involves loading a fiber reinforcement preform into a mold cavity, closing the mold, injecting resin into the mold and allowing the resin to cure. To study the resin transfer molding process and issues affecting it, a laboratory containing an experimental RTM apparatus has been established. The apparatus has a glass window to observe the mold filling process and can incorporate various mold shapes such as a quasi-2D panel, a 3-D rectangular section and a 3-D semicircular section. To characterize the flow through the molds a commercial CFD software has been used. This thesis describes the establishment of this laboratory and preliminary studies that have been conducted.

Advanced composite materials are becoming increasingly more valuable in a plethora of engineering applications due to properties such as tailorability, low specific strength and stiffness and resistance to fatigue and corrosion. Compared to more traditional metallic and ceramic materials, advanced composites such as carbon, aramid or glass reinforced plastic are relatively new and still require research to optimize their capabilities. Three areas that composites stand to benefit from improvement are processing, damage detection and life prediction. Fiber optic sensors and piezoelectric transducers show great potential for advances in these areas. This dissertation presents the research performed on improving the efficiency of advanced composite materials through the use of embedded fiber optic sensors and surface mounted piezoelectric transducers. Embedded fiber optic sensors are used to detect the presence of resin during the injection stage of resin transfer molding, monitor the degree of cure and predict the remaining useful life while in service. A sophisticated resin transfer molding apparatus was developed with the ability of embedding fiber optics into the composite and a glass viewing window so that resin flow sensors could be verified visually. A novel technique for embedding optical fiber into both 2- and 3-D structures was developed. A theoretical model to predict the remaining useful life was developed and a systematic test program was conducted to verify this model. A network of piezoelectric transducers was bonded to a composite panel in order to develop a structural health monitoring algorithm capable of detecting and locating damage in a composite structure. A network configuration was introduced that allows for a modular expansion of the system to accommodate larger structures and an algorithm based on damage progression history was developed to implement the network. The details and results of this research are contained in four manuscripts that are included in Appendices A-D while the body of the dissertation provides background information and a summary of the results. / Graduate

The resin transfer molding (RTM ) process, in which a thermosetting resin is injected into a mold cavity preloaded with a porous fiber preform, is a manufacturing method for producing advanced continuous fiber reinforced composite products with complex geometries. Numerical simulation of resin transfer molding process is an often needed tool in manufacturing design, in order to analyze the process before the mold is constructed. In this study, a numerical simulation of the resin impregnation process in RTM of composite materials is performed by using and modifying an existing simulation program. The parts that are molded in the simulations have their planar dimensions much larger than their thicknesses. Therefore, the mold filling process can be modeled as two dimensional by neglecting the variations along the thickness direction. The program is capable of simulating two-dimensional, isothermal impregnation processes through orthotropic fiber preforms of planar but complex geometries. The formulations of the physical problem, used in this study, were taken from the theory of macroscopic flow through anisotropic porous media. The formulated governing equation and boundary conditions are solved in a regular-geometry computational domain by transformation through boundary fitted coordinate system. The discretization for numerical solution is performed by the finite difference method. The current study extends the existing capabilities of the simulation program by enabling the simulation of impregnation through non-homogeneous fiber preforms. Furthermore, the capability to simulate injection from two gates (as opposed to a single gate injection that existed before) is developed and added to the program. Various one-dimensional impregnation simulations (as parametric studies) are performed to assess the influence of process parameters. Results are also compared with analytical solutions and found to be in agreement with them. Two-dimensional impregnation simulations are performed for a planar, complex geometry mold. The two-dimensional results are compared with experimental results from the literature and are found to be in acceptable agreement with them. In addition to the study of various parametric variations in two-dimensional impregnation, double-gate resin injection simulations are performed and discussed as well.

Composite materials have the potential to revolutionize life in the 21st century. They are contributing significantly to developments in aerospace, hydrogen fuel cells, electronics and space exploration today. While a number of composite material processing methods exist, resin transfer molding (RTM) has the potential of becoming the dominant low-cost process for the fabrication of large, high-performance products. RTM has many advantages over alternative processes, including the capability of producing complex 3D shapes with a good surface finish, the incorporation of cores and inserts, a tight control over fiber placement and resin volume fraction and the possibility of embedding sensors into manufactured components for structural health monitoring. Part of the reason RTM has not received widespread use is due to its drawbacks such as its relatively trial and error nature, race tracking, washout, high cycle time and void formation. The basic operation of the process involves loading a fiber reinforcement preform into a mold cavity, closing the mold, injecting resin into the mold and allowing the resin to cure. To study the resin transfer molding process and issues affecting it, a laboratory containing an experimental RTM apparatus has been established. The apparatus has a glass window to observe the mold filling process and can incorporate various mold shapes such as a quasi-2D panel, a 3-D rectangular section and a 3-D semicircular section. To characterize the flow through the molds a commercial CFD software has been used. This thesis describes the establishment of this laboratory and preliminary studies that have been conducted.