Viscoplastic tearing of polyethylene thin film

Recent advances in non-contact strain measurement techniques and large-strain constitutive modeling of the Linear Low-Density Polyethylene film used in NASA Superpressure balloons, StratoFilm 420, are combined to provide a novel measurement technique for the tear propagation critical value of the J-integral. Previously these measurements have required complex test configurations and procedures. It is found that the critical value of the Jintegral increases by approximately 50% when the strain rate is decreased from 1.33 × 10−4 s−1 to 1.33 × 10−5 s−1. It is shown that there is good correlation between measurements made on uniaxially loaded dogbone samples and circular diaphragms loaded by pressure, both with a 2 mm wide slit in the middle. This result indicates that more extensive studies of strain-rate dependence may be made with the simpler, uniaxial test configuration.