Effect of the testing geometry on the applicability of the load separation criterion in determining the fracture resistance (JIc) of ductile polymers.

The analysis of the specimen geometry effects on the evaluation of material fracture resistance plays a fundamental role in the development of fracture mechanics testing methods, typically aimed at determining intrinsic material properties. In this work, the applicability of a procedure based on the load separation criterion in determining the fracture resistance (JIc) of an acrylonitrile-butadiene-styrene (ABS) resin was analysed and discussed. In particular, the effects of the specimen dimensions were investigated. Several sets of single edge notched in bending [SE(B] specimens, that differed for specimen dimensions, were tested. Each set consisted in a series of specimens with different initial crack length to width ratio. The existence of a separable blunting region, necessary condition for the application of the load separation criterion, was ascertained for each specimen geometry considered. The data of J at fracture initiation, JIc, obtained by applying the methodology based on the load separation criterion, resulted remarkably dependent on a0/W for each set of specimens of given dimensions. At a fixed a0/W, also the specimen dimensions (thickness and width) were found to have an effect on the fracture resistance. These data of JIc were also compared with those resulting from the application of a multi-specimen methodology.