THE EFFECT OF COOLING RATE ON FREE-EDGE STRESS DEVELOPMENT IN SEMICRYSTALLINE THERMOPLASTIC LAMINATES

A numerical model is developed for prediction of the process-induced t hermal residual stresses in thermoplastic composite laminates. The mod el addresses the development of the three-dimensional residual stress state in fracture-critical free-edge regions as well as through-thickn ess stress variations. The current approach and analysis provide a uni que capability for the investigation of the influence of thermal proce ssing and structural parameters on the resulting buildup of residual s tresses during manufacturing. Therefore, it can assist in the design a nd analysis of thermoplastic composites in terms of tailoring of mecha nical and strength characteristics. The applied surface cooling rate f rom the melt has a strong effect on the free-edge stress levels obtain ed at room temperature, and in particular the interlaminar stresses. R esults are shown for the case of typical cross-ply and quasi-isotropic APC-2 (graphite/polyetherether-ketone) laminates.