Mechanics and mechanisms of impact fracture in semi‐ductile polymers

The method proposed by C. E. Turner and J. G. Williams for characterizing the impact resistance of polymers was reanalyzed and a new method has been developed for the study of semi‐ductile polymers. In these polymers, the fracture occurs by a set of stable and unstable crack propagation stages. The new model takes into account the first stable stage and the point of instability in order to allow the determination of two fracture energies Ḡ st and G inst . These fracture parameters characterize the material impact behavior. The model has been applied to polyamide 11 and 12. Molding condition and orientation effects on the impact fracture energies are presented.