Analyse expérimentale et numérique de la fabrication de pièces composites par le procédé RTM

Cette thèse s intéresse à la fabrication de pièces composites par le procédé Resin Transfert Molding (ou RTM), appliquée à des tubes de protection thermiques. Plus particulièrement, cette thèse vise à démontrer la faisabilité d utiliser ce procédé pour la fabrication cette pièce complexe. La phase d imprégnation de préformes sèches est plus particulièrement étudiée. Après mise en oeuvre, cette pièce peut présenter des défauts tels que de la porosité ou des déplacements de plis constituant la préforme. L objectif de cette thèse est donc de comprendre l origine de ces défauts et de minimiser voire de d empêcher leur apparition. Pour cela, une démarche expérimentale a été mise en place. Celle ci comprend la réalisation d un pilote de laboratoire permettant d appliquer différentes conditions d imprégnation aux préformes considérées. La perméabilité des renforts considérés a aussi été évaluée à différentes échelles grâce à l utilisation de moyen dédiés à l échelle macroscopique (banc de perméabilité planaire et transverse), et grâce à l utilisation d un code de calcul se basant sur des images de tomographie synchrotron à l échelle microscopique. Enfin, une analyse de la qualité des prototypes réalisés a été menée en suivant des procédures mises en place lors de ce projet et les résultats analysés et mis en relation avec les conditions de mise en oeuvre. Cette approche expérimentale est couplée aux simulations numériques de la phase d imprégnation que nous avons aussi mise en oeuvre au cours de cette thèse. Par l utilisation combinée de la simulation numérique et des essais expérimentaux, nous avons défini des critères estimant le risque d apparition des défauts. Ces critères ont montré leur efficacité sur les solutions innovantes que nous avons proposées puisque répondant aux exigences du cahier des charges industriel.This work concerns the manufacturing of composite parts using the Resin Transfer Molding (RTM) process. A major goal of this study is to test the feasibility of using this process to manufacture a thick tubular part with a complex shape. This study concerns the different stages of the process with an important focus on the injection step of dry preforms. The goal of this thesis is to understand the generation of manufacturing defect (mainly porosity and preform deformation) that possibly takes place during the injection step to avoid them. An experimental procedure is proposed. An experimental setup was developed to study the influence of the different process parameters on the quality of the composite parts. The determination of the longitudinal and through the thickness permeabilities was conducted experimentally on sheared and un-sheared samples. An alternative technique to estimate the permeability is presented based on simulation software using X-ray tomography images at the microscale. At last, a quality control procedure was developed and applied to the tubes manufactured within this project. This experimental work was compared to numerical simulations of the injection stage. Using both numerical simulations and experiments, criteria on process and material parameters to predict the quality of the tailored parts are presented. Those criteria are successfully compared to experimental data and were applied to design innovative injection solutions that meet industrial specifications.ORLEANS-SCD-Bib. electronique (452349901) / SudocSudocFranceF

Preparing an Organization for Sustainability Transitions-The Making of Boundary Spanners through Design Training

Organizations today need to adapt their operations for a more sustainable future, and the transition management literature has highlighted the need for individuals who can collaborate with others to find new paths forward. Essentially, these individuals are boundary spanners with specific skills and competences to bridge diverging perspectives and facilitate knowledge dissemination and integration. Such individuals become critical change agents in organizations and essential in preparing the organization for sustainability transitions. The purpose of this study is to explore how organizations can enable and encourage individuals to take on this role and develop the skills and competences needed to become boundary spanners. Based on a case study set in a large Canadian energy corporation striving to shift towards more sustainable operations, our paper explores the emergence of boundary spanners, focusing on the effects of a design training program in supporting such roles in the organization. Our findings outline essential characteristics of boundary spanners; through illustrative career trajectories of four individuals participating in the training program, we show how the training program contributed to the emergence of boundary spanners.Funding Agencies|FRQSC [205466]; Chalmers University of Technology, Area of Advance Energy: post-doc grant in 2016</p

Study of the galvanic corrosion in Al/CFRP co-cured hybrid materials

International audienceThe use of hybrid structures where the right material is used at the right place for its best properties is of great interest for structures optimisation, particularly when mass reduction is required. In such hybrid structures, where metal and composite are closely in contact, the strength of the interface between the metal and the composite can be altered by the galvanic corrosion between the aluminium and the composite when Carbon Fibres Reinforced Plastic (CFRP) is used. This paper is related to the corrosion and mechanical properties of an Aluminium/CFRP co-cured hybrid structure. The influence of the aluminium surface treatment on the interface properties obtained after a one step co-curing manufacturing process has been assessed. Al-2024 aluminium alloy treated by either tartaric-sulphuric anodizing (TSA), chromic acid anodizing (CAA) or silane pre-treatment (γ-GPS) has been used and co-cured with CFRP. The galvanic corrosion behaviour of the Al/CFRP hybrid system has been determined with the Evans diagram method and the mechanical strength of the interface has been characterized with a single-lap joint tensile test before and after exposure of the samples in a salt spray chamber. The different surface treatments of the aluminium alloy have been compared in term of both galvanic corrosion and adhesion properties before and after corrosive environment exposure in order to find the best compromise for Al/CFRP structure applications

Characterisation and modelling of thermal expansion coefficient of woven carbon/epoxy composite and its application to the determination of spring-in

International audienceProperties of resin and composite, especially anisotropic coefficients of thermal expansion, are very crucial to precisely determine residual stress generated in a composite part. No comprehensive study is available in the literature to determine these properties for woven composites and then its application to model residual stress in woven carbon epoxy composite parts. In the present article, experimental results on thermal coefficients of RTM6 epoxy resin as well carbon/epoxy woven composites obtained using different experimental techniques are compared with homogenised coefficients of thermal expansion results. Evolution of spring-in angle of L-shaped carbon/epoxy woven composite (during and after cure) with three different thicknesses is modelled by simultaneously solving the thermal-kinetics and thermal-chemical-mechanics coupling by using finite element code COMSOL Multiphysics. Objective was to quantify the contribution of curing and cooling to the formation of residual stress. Anisotropic properties of composite, during and after cure, required for numerical simulation are obtained using an analytical method. Variation in properties with degree of cure and thermal gradients induced in the part during fabrication are considered while modelling. Modelled properties of cured composites were compared with experimental values and were found in agreement. The spring-in angle values obtained by numerical simulation are compared with the results of the analytical model as well as experiments. Effect of variation of fibre volume fraction and presence of thermal gradients on spring-in was studied as well

Modelisation du procédé d'infusion par une méthode multicouche

International audienceVacuum-assisted resin transfer molding (VARTM) is a very suitable solution for composite manufacturing industry. It allows the manufacturing of large and complex shape parts at low costs. However, the simulation of this process is complicated due to myriad physical phenomena involved, specifically the strong coupling between the resin flow and the preform compressibility, i.e. hydro-mechanical coupling. Moreover, the use of the distribution medium involves two types of flow: Planar flow and through-the-thickness flow. These flows cannot be considered together by a 2D model. On the other hand, 3D models require an important amount of computation time. This article presents a VARTM modeling approach that takes into account the hydro-mechanical coupling and the coexistence of planar and transverse flows. The proposed modeling approach allows the simulation of the infusion process in the case of multilayer preform with different materials and orientations, including the distribution medium. This model is validated experimentally based on several infusions

INJECTION OF A COMPLEX PREFORM BY RTM. OPTIMISATION OF A MOULD DESIGN AND PROCESS PARAMETERS

International audienceThis work concerns the manufacturing of a composite tube using RTM process. During the preforming stage, a woven braid is laid down and stacked on a mandrel so that reinforcement plies form conical shapes with a defined angle. An innovative experimental preforming procedure has been developed to respect the specific angle. The resin injection step has been studied both experimentally and numerically. In this work a focus is applied on the optimization of the mould geometry and on the way the resin is injected within the preform to prevent the appearance of defects such as displacement of plies and porosity. Different optimization steps are described in this work and a mould geometry is proposed for this specific application and the quality of the part obtained is discussed and analysed

Preform permeability measurement and 3D resin flow simulation for dry AFP

International audienceAn efficient experimental method is proposed to measure very low permeability of composite laminated preform fabricated by automated dry fiber tape placement. A new computer program is also presented for the numerical simulation of three dimensional resin flow which is generally impossible by conventional commercial packages due to an extremely heavy computing cost