Viscoplastic tearing of polyethylene thin film

Recent advances in noncontact 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 required complex test configurations and procedures. It is found that the critical value of the J-integral 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