eFfects of fORming dEfects on the meChAnical responSe of composiTe structures – FORECAST

The composite material arises simultaneously with the structure during the realisation of the part. Any defect caused during implementation can affect the mechanical strength of the structure. This work focuses on the effects of defects generated during the forming of dry preforms and their consequences on the final properties of the composite structure after resin impregnation. While many studies have addressed the forming defects of dry preforms, the literature is scarce on the effects of these defects and the need to model them. Two aspects are the subject of this research. The first, very experimental, seeks to identify forming defects by integrating originality during the process: the monitoring, in-situ, of the deformability of the preform by integrating piezo sensors at the heart of the reinforcement in order to refine the understanding of the formation of defects. After resin impregnation, the defects will be tomographed in order to generate a voxel model that can be used by the second part of this research. The composites obtained will be tested experimentally in order to analyse the implication of defects on the durability of the structures. Here too, the piezo sensors at the heart of the composite will allow better monitoring of damage mechanisms. The second part of this research addresses the modelling aspects. It is a question of simulating the forming defects, calculating the residual stresses resulting from the deformation of dry fabrics and verifying, by comparison with the experiment, the validity of the approaches used. Then the study will move towards the modelling of the composite in the presence of forming defects. The approach used will be based on the mesoscopic scale phase field method and taking into account the residual stresses previously calculated. A permanent dialogue between tests and calculations will ensure the validity of the approaches that will be developed.