Study of Photoplastic Behaviour of Polycarbonate using Digital Image Correlation

Earlier studies on photoplastic behaviour of polycarbonate are limited to the strain at which the localized yielding (necking) initiates (about 6% strain). In this study, the photoplastic behaviour of polycarbonate is studied using digital image correlation (DIC). Two cases are considered: one in which no localized yielding is observed and the other in which initiation and propagation of the localized yielding is observed. For the first case, a modified dog bone specimen is proposed to evaluate the photoplastic constant. In the second case, a conventional tensile test specimen is used. Both photoplasticity (transmission and reflection) and DIC experiments are performed on the specimens to determine the relation between fringe order and principal strain difference for strains of up to 60%. It is observed that the photoplastic constant is a function of strain. Finally, the behaviour of the tensile test specimen is numerically simulated. The true stress-strain curve of polycarbonate needed for FE simulation is determined using DIC experiments on the standard tensile test specimen. By post-processing the FE results, isochromatic fringes are plotted and compared with experimental results.