Three dimensional finite element investigations into the effects of thickness and notch radius on the fracture toughness of polycarbonate

Fracture toughness of polycarbonate (PC), a commercially important glassy amorphous polymer, is known to be sensitively dependent on a number of factors including molecular weight, ageing time, loading rate and specimen geometry. In this work, we analyze the effect of notch radius and specimen thickness on the near tip fields and the consequence of these on the mode I fracture initiation. To this end, we have performed extensive three dimensional Finite Element simulations within the framework of large deformation elasto-plasticity based on a realistic constitutive model that has been carefully calibrated for PC. Using a simple set of criteria for fracture initiation by void nucleation or ductile tearing, we are able to reproduce experimentally observed brittle to ductile transitions that occur in PC with decrease in thickness and increase in notch radius.