Process-induced residual stress in polymer-based composites

The consolidation of a polymer based composite part is usually accompanied by the build-up of the stresses and deformations that are caused mainly by the polymer matrix shrinkage, the resin rheological and mechanical properties changes associated to the advancement of the cure reaction and by the material properties mismatch of the system constituents, mold, fibers reinforcement and thermoset resin. These process-induced residual stresses and strain are obviously undesired phenomena that should be avoided leading to low performance, shape distortions, warpage, matrix cracks and delaminations. Therefore, the optimization of the manufacturing cycle coupled to the capability to predict and measure the processing residual stress and strains represent important issues to be addressed. In this work, after a preliminary introduction on the most relevant mechanisms inducing the formation of stresses and strains in polymer-based composite parts, the most recent advances both in the modeling of the cure-induced residual stresses and strains build-up and in the experimental techniques for their measurement are presented.