Discussion of impact fracture parameters in ductile polymers

Discussion is given of an energy-based two-fracture parameter model proposed recently by T. Vu-Khanh to characterize the impact fracture of ductile polymers. It is shown that such a model is equivalent to an earlier essential work of fracture analysis given by the author and his co-workers. Whilst the specific essential fracture work, either for fracture initiation or propagation is a material constant for a given sheet thickness, the equivalent tearing modulus is not a material property and it depends on specimen geometry.