The tensile force oscillation of polycarbonate at elevated temperatures



Tensile testing of polycarbonate (PC) with and without gamma-ray irradiation at elevated temperatures was investigated. Two deformation mechanisms, the shear bands at low temperatures and the craze formation at high temperatures accompanied with force oscillation, were responsible for the deformation. The tensile force oscillation was observed during the tensile testing in air, but not in water or oil. This difference is attributed to the periodic variation in the elastic modulus of PC, caused by local temperature change during the deformation process. Note that air is a poor medium for heat conduction, whereas water and oil are good conductors. In addition to the test environment, the effect of the crosshead speed on the force oscillation was also investigated. The oscillation was preferably observed at lower crosshead speeds within the testing range, and was more pronounced for the irradiated specimens. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers