The role of ultimate elongation in the determination of valid ligament range of essential work of fracture tests

In this study, the feasibility of a previously proposed ultimate elongation-based criterion of essential work of fracture (EWF) method was reconsidered for several materials. Suitable ductility level (DL) ranges for the EWF testing of polymers were discussed, too. It was shown that there is a relationship between the DL terms and the experimentally estimated crack opening displacement values. Based on Coterell’s estimate of the size of the fracture process zone a lower ligament limit of EWF concept was also presented. This lower bound should be considered for thin samples where the original thickness-dependent criteria seemed to be not severe enough.