Brittle-Ductile Transition of a polymer glass in the presence of a crack

Fracture behavior of polymer glasses under deformation has been widely studied in the experiment. However, molecular-level understanding of crack propagation in polymer glasses is still lacking. In this work, the standard bead-spring model based molecular dynamic simulation was modified to gain microscopic insights into the crack propagation in glassy polymers. In the presence of a pre-existing crack, the transition from brittle failure to shear yielding in extension was investigated by varying the temperature, the length of the pre-crack length and deformation rate. The results from the simulation are consistent with experiment. Our simulation results also show that the brittle-ductile transition temperature is strongly dependent on the strength of the pair potential.