Long-term failure of transversely loaded glass/iPP

Herein, temperature-dependent long-term behavior of polypropylene and its transversely loaded unidirectional glass fiber reinforced composite is investigated and a lifetime prediction method is proposed, which is based on the observed long-term failure mechanisms. Furthermore, the effect of cooling rate during processing on the time-dependent behavior is addressed. The composite is revealed to exhibit multiple molecular deformation mechanisms, similar to neat polypropylene, which is modeled using the Ree–Eyring approach. Failure kinetics under constant-strain-rate and creep tests are found to be identical and switching from creep to cyclic loading decelerates the failure, which are signs of plasticity-controlled failure. Hence, lifetime is predicted well by using a lifetime prediction methodology for the plasticity-controlled failure which combines the Ree–Eyring approach and the concept of critical strain. A change in the cooling rate alters the deformation and failure kinetics: lower cooling rates promote embrittlement.