Le travail présenté dans ce manuscrit consiste en une contribution à l'étude de ces structures RTM par microscopie Raman, afin de mesurer certains paramètres tel que la réticulation, l'identification de composés chimiques, les contaminations, l'homogénéité d'additifs… mais aussi sur l'utilisation de ces mesures dans le cadre d'une modélisation numérique de ces structures. Cette Thèse de Doctorat s'inscrit dans un programme pour le remplacement des mesures actuelles intrusives, destructives et indirectes par une mesure in situ via un capteur Raman implanté dans l'outillage et à la construction du système en milieu industriel. Avec comme but d'optimisation par exemple les procédés de fabrication des pales d'éolienne, ponts de bateaux de garantir et valider des critères de qualité des pièces techniques à forte valeur ajoutée et enfin d'optimiser les caractéristiques physico-chimiques liées à la mis en œuvre dans l'outillage / The work presented in this manuscript is a contribution to the study of these structures RTM Raman microscopy, to measure parameters such as curing, the identification of chemical compounds, contamination, uniformity as addenda but ... also on the use of these measures in the framework of a numerical modelling of these structures. This Thesis is a program for replacing the current intrusive, destructive and indirect measurement in-situ Raman via a sensor implanted in the equipment and system construction in an industrial environment. With the aim of optimization processes such as manufacturing wind turbine blades, bridges boat guarantee and quality criteria of technical parts with high added value and to optimize the physical and chemical related to the mission implemented in tooling.

Le travail présenté dans ce manuscrit consiste en une contribution à l'étude de ces structures RTM par microscopie Raman, afin de mesurer certains paramètres tel que la réticulation, l'identification de composés chimiques, les contaminations, l'homogénéité d'additifs... mais aussi sur l'utilisation de ces mesures dans le cadre d'une modélisation numérique de ces structures. Cette Thèse de Doctorat s'inscrit dans un programme pour le remplacement des mesures actuelles intrusives, destructives et indirectes par une mesure in situ via un capteur Raman implanté dans l'outillage et à la construction du système en milieu industriel. Avec comme but d'optimisation par exemple les procédés de fabrication des pales d'éolienne, ponts de bateaux de garantir et valider des critères de qualité des pièces techniques à forte valeur ajoutée et enfin d'optimiser les caractéristiques physico-chimiques liées à la mis en œuvre dans l'outillage.

RTM6 has for more than 20 years been the main commercial epoxy system for infusion processing qualified by the aerospace industry. In common with other aerospace-grade epoxy systems RTM6 is mechanically strong but brittle, producing carbon-fibre (CF) composites with relatively low impact resistance and damage tolerance. This thesis reports an approach to toughening epoxy-CF composites without modification of the resin. Thus, a T300 carbon fabric (ES-fabric) coated with 20 weight % of a poly (aryl ether ketone) (PAEK) was used to toughen the composite. The initial stage of the study was the manufacturing process. DSC and oscillatory-shear rheology were used to determine flow times and cure conditions, and to produce laminates with fibre volume fractions ≥55% a hybrid resin infusion/hot-press process was developed. Dynamic mechanical thermal analysis also showed that the PAEK coating produced relatively little plasticization of the epoxy matrix, with values of the matrix glass transition temperature shifting from 186±4.4 to 181± 1.4 ºC when using the ES-fabric. The main body of the study focussed on the toughening effect afforded by the PAEK coating relative to an uncoated fabric system as a reference. Mode I and Mode II interlaminar fracture toughness behaviour were studied using dual cantilever beam (DCB) and four-point end-notch flexure (4ENF) tests, respectively. The measured mode-I fracture energy, GIC, increased three-fold, from 216 ± 7.2 Jm-2 to 751 ± 105 Jm-2, due to the toughening effect of the PAEK coating; whereas the mode-II fracture energy, GIIC, increased almost four-fold from 857 ± 99 Jm-2 to 3316 ± 372 Jm-2. Damage resistance was studied using low-velocity impact testing and damage tolerance using a miniature compression-after-impact (CAI). A comparative study of damage tolerance was performed using open-hole compression (OHC) testing. The impact damage resistance significantly improved with the use of the PAEK-coated ES-fabric as well as the CAI and OHC behaviour. Impact testing showed the PAEK -toughened system exhibited higher energy abortion than the untoughened system, larger damage area was created in the T300/RTM6-2 after impacted with same energy. The CAI results indicated that the normalized CAI strength is major related that damage width rather than other factor. OHC results are predicted by using W-N criteria, for ES/RTM6-2: ASC a0 = 9.35 mm and PSC d0 = 2.72mm; whereas for T300/RTM6-2: ASC a0 = 7.95 mm and PSC d0 =2.43 mm, indicates that the compressive strength of T300/RTM6-2 is more sensitive to the size of the hole, thus ES/RTM6-2 perform better damage tolerance. The results from mechanical testing indicate that the PAEK coating toughened the composite system and significantly improved damage tolerance. Scanning electron microscopy indicated that these improvements in fracture behaviour were due to morphological changes induced by the PAEK coating in the matrix-CF interfacial region, where such changes can provide the maximum benefit. Small particles of RTM (approximately 1 µm in diameter) were observed imbedded within a continuous PAEK phase. Thus, during testing crack propagation was deflected (or bifurcated) by the RTM6 particles or stopped by shearing of the continuous PAEK phase of this multiphase region. This morphology is proposed to have formed in the interfacial region during processing by dissolution of the PAEK coating within the matrix resin system, followed by reaction-induced phase separation and then phase-inversion as the matrix cures.

In response to serious environmental and economic concerns, the design and production of aircrafts have been changing profoundly over the past decades with the nose-to-tail switch from metallic materials to lightweight composite materials such as carbon fibre reinforced plastic (CFRP). In this context, the present doctoral research work aimed to contribute to the development of a CFRP booster casing, a real innovation in the field initiated and conducted by Safran Aero Boosters. More specifically, this thesis addresses the matter of joining metal/CFRP hybrid structures, which are prone to possibly detrimental residual stresses.The issue is treated with an approach combining experimental characterisation and finite element (FE) simulations. The multi-layered system’s state of damage was systematically examined on hundreds of micrographs, and the outcome of this study is presented under the form of a statistical analysis. Further, the defects’ 3D morphology is investigated by incremental polishing. A number of thermal and mechanical properties are measured by diverse physical tests on part of the constituent materials, i.e. the aerospace grade RTM6 epoxy resin, the structural Redux 322 epoxy film adhesive, and AISI 316L stainless steel. They are used as input data in a FE model of the multilayer that is developed and progressively refined to obtain detailed residual stress fields after thermal loading. These results are compared to experimental data acquired by X-ray diffraction stress analysis and with the curvature-based Stoney formula. Cohesive elements are placed at specific locations within the FE model to allow simulating progressive damage. Peel tests, mode I, mode II and mixed mode I/II fracture tests are thus performed in view of measuring the joint toughness. The results of these tests are discussed and the presence of residual stress in the fracture specimens is highlighted. Key information for the calibration of the cohesive law is finally identified via inverse FE analysis of the mode I test, this being a significant step in the process of building a damage predictive FE model of the multi-layered system. / Doctorat en Sciences de l'ingénieur et technologie / info:eu-repo/semantics/nonPublished