Evaluation of crack propagation behavior of porous polymer membranes

Abstract

Abstract This study experimentally and numerically investigated the crack propagation behavior of porous polymer membranes in order to identify the criterion for crack propagation. A notch was introduced into the membrane as an initial crack (pre-crack), and a uniaxial loading was applied to produce stable crack propagation. During the test, crack propagation was observed using a CCD camera and the digital image correlation (DIC) method. The strain around the pre-crack tip at the onset of crack propagation was measured experimentally using the DIC method. We found that large-scale yielding developed before crack propagation. Stable crack propagation was observed for all tensile tests. In parallel, a homogeneous model that mimicked the porous polymer membrane was created using the finite element method (FEM) to investigate the stress/strain distribution around the crack tip. This study adopted the yield criterion proposed by Deshpande and Fleck. The computed strain distribution was compared with the experimental results, and the distributions were found to be similar. The strain distribution obtained by the DIC method and FEM computation yielded a J-integral value, which could be used to investigate the criterion for crack propagation. Regardless of the initial crack length, the J-integral value at the onset of crack propagation was a constant value for all tests. We concluded that we successfully determined the criterion for crack propagation in the porous polymer membrane. Our comprehensive study using DIC experiments and FEM computations is useful for identifying the crack propagation behavior of a porous polymer membrane and for determining the criterion for crack propagation.