As an example, let us consider a 4mm thick composite section with the skin-core microstructure. The skin thickness at the bottom is fixed at 1mm, while the thickness of the top skin is varied between 0 and 1mm. Thus, we have seen that the presence of a reinforcing glass phase, the crystallization process and the skin-core microstructure typical of injection molded composites, all increases the residual stress state in the material. Further, an important observation was even on slow cooling, significant residual stresses can persist in materials with the skin-core microstructure. Glass reinforcement phase increases the level of residual stresses.
Crystallization increases residual stress.
Asymmetry in the microstructure and thermal history can result in warpage.