Some observations on fatigue and crazing of polycarbonate (bisphenol A)

Abstract

Amorphous, unoriented polycarbonate (bisphenol A) films are cyclically fatigued at several tensile stress levels below their yield stress. The fatigued films have been investigated by X-ray scattering, density measurements, and dynamic mechanical tests (Rheovibron). The X-ray data suggest a decrease of the interchain distances in the fatigued films by about 1 %. In spite of this improved packing the overall density shows a decrease (of 0.08 %). The dynamic mechanical testing reveals shifts of both the α and β relaxation peaks towards lower temperatures. In addition, many of the fatigued film samples fracture at the cryogenic temperatures during the tests on the Rheovibron. These results lead to the conclusion that microvoids are formed in the fatigued polymer. The microvoids are distributed throughout the fatigued polymer and weaken the material.