Out-of-autoclave manufacturing of complex shaped composite laminates

Out-of-Autoclave (OOA) manufacturing answers the growing need of the aerospace industry to process components of larger sizes at reduced costs. Recent prepreg materials have been developed specifically for OOA manufacturing and feature increased in-plane permeability through the presence of dry-fibre paths for efficient evacuation of gases. However, the differences in impregnation and resin kinetics attributed to OOA prepregs with respect to autoclave prepregs may affect the compaction behaviour in complex shape laminates. This thesis presents the results of an investigation of important design and processing parameters on the quality of complex shape laminates manufactured by OOA methods.L-shape composite laminates were manufactured by OOA methods, following the recommendations documented in the literature. The samples were tested for thickness variation at the corner and void content levels. The thickness variation at the corner was characterised based on the radius-to-thickness ratio for Cytec Cycom 5320 PW and 8HS prepregs with concave and convex tools. The experimental study showed increased corner thickening with decreasing radius-to-thickness ratio for both tool shapes. The data can be used to determine the minimal radius-to-thickness ratio for acceptable thickness variation for each material and serve as a design guideline. An analytical model of the compaction of L-shape laminates was developed. The discrepancies between the experimental data and the model predictions for thickness variation at the corner highlight the importance of shearing mechanisms in the compaction of L-shape laminates. Also, from the experimental investigation of various bagging arrangements, it is observed that the compaction at the corner is improved with the use of a pressure intensifier or pressure strip with proper corner radius. In addition, breather material should be placed under the pressure intensifier to allow efficient air removal and maintain a low void content level. A numerical analysis of the compaction of a laminate over a concave tool was performed and demonstrated that the material of the pressure intensifier or pressure strip should be of high stiffness for efficient laminate compaction.%%%%L'industrie aerospatiale recherche davantage a fabriquer des pieces en materiaux composites de plus grandes dimensions. Ceci peut etre accompli a plus faibles couts par le procede de fabrication hors-autoclave. Les materiaux pre-impregnes utilises pour ce procede sont semi-impregnes et donc, dotes d'une section de fibres seches qui permet l'evacuation des bulles d'air et de gas avant la consolidation du lamine et la polymerisation de la resine. Cependant, le comportement en compaction de ces materiaux sur des moules complexes peut etre tres different de celui des materiaux pre-impregnes pour autoclave, vu le plus faible niveau d'impregnation et une differente cinetique de reaction de la resine. Cet ouvrage presente les resultats de l'etude de la qualite de pieces complexes fabriquees par le procede hors-autoclave. L'influence du…