Short-to long-term deformation behavior of glassy polymers under cyclic uniaxial, torsional, and multiaxial loads

Abstract

Despite the popularity of glassy polymers, the research of their short-to long-term fatigue resistance has been consider-ably limited to date. In this research, both an enhanced molding equipment and a model are proposed to investigate the resistance of glassy polymers (polycarbonate, PC) under cyclic fatigue loads. Two failure mechanisms consider the low-cycle and high-cycle regimes, respectively: plastically induced (including the effect of free volume) and fatigue. Therefore, the proposed model is history dependent. Contrast to state-of-the-art models, the proposed model is capable to simulate the experimentally observed ultralow-to high-cycle fatigue life, suggesting that the model is a valid tool for simulating time-consuming and costly tests. It is noteworthy that the predicted progress of material damage was found to resemble the observed development of accumulated void volume. The damage development significantly affected the onset and growth of tertiary cyclic creep and thus, the length of fatigue life. The amorphous microstructure also appeared to firmly resist failure under torsion and better than under uniaxial loads.