Measurement and prediction of residual strains and stresses during the cooling of a glass fibre reinforced PA66 matrix composite
Résumé
The forming process of thermoplastic composites inevitably leads to the development of residual stresses. This study proposes a model to predict the residual stresses at the ply level of a thermoplastic composite. It accounts for heat transfer, crystallization kinetics and the mechanical behaviour of the laminate. The model is applied to the cooling of a polyamide 66 (PA66) matrix reinforced with continuous glass fibres. The Stress Free Temperature is considered as the starting point of stresses accumulation within each ply. It is experimentally identified by monitoring the curvature evolution of composite coupons with temperature, leading to a temperature of 200°C. The evolution of the curvatures of [90404] laminates are recorded with a digital image correlation technique. They are compared with the curvatures predicted with the model, which permits to validate it. The predicted stresses distribution is then discussed, as well as the impact of several parameters on the stresses intensity.
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