Effect of thermal pretreatment on the fracture behavior of polycarbonate in medium strain rate tensile tests



The fracture properties of as-received and annealed (48 h at 403 K) commericial polycarbonates (PC) were examined in tensile tests with an average strain rate of ė = 2 s−1. Both materials were subjected to tensile tests at temperatures ranging from 223 to 423 K. The results were processed by a computer interfaced to the testing machine. The tensile strength of the annealed (pretreated) PC was superior to that of the as-received (untreated) material. The elongation at break and the fracture energy, then, decreased due to annealing at all temperatures, yet followed impact strength curves. Fracture analysis and fracture morphology revealed clear differences in the behavior of the materials. Fracture nucleation occurred commonly at several points in the pretreated specimens, whereas only one nucleation point was found in the untreated specimens. Shear yielding morphology, which indicated plastic deformation, started to appear at a lower temperature in the pretreated specimens than in the untreated ones.