Evaluation of J-initiation fracture toughness of ultra-high-molecular-weight polyethylene used in total joint replacements

Fracture of ultra-high-molecular-weight polyethylene (UHMWPE) total joint replacement components is a clinical concern. Thus, it is important to characterize the fracture resistance of UHMWPE. To determine J-initiation fracture toughness (JQ) for metals and metallic alloys, ASTM E1820 recommends a procedure based on an empirical crack blunting line. This approach has been found to overestimate the initiation toughness of tough polymers like UHMWPE. Therefore, in this study, a novel experimental approach based on crack tip opening displacement (CTOD) was utilized to evaluate JQ of UHMWPE materials. J-initiation fracture toughness was experimentally measured in ambient air and a physiologically relevant 37 °C PBS environment for three different formulations of UHMWPE and compared to the blunting line approach. The CTOD method was found to provide JQ values comparable to the blunting line approach for the UHMWPE materials and environments examined in this study. The CTOD method used in this study is based on experimental observation, and thus, does not rely on an empirical relationship or fracture surface measurements. Therefore, determining JQ using the experimentally based CTOD method proposed in this study may be a more reliable approach for UHMWPE and other tough polymers than the blunting line approach.