CHARACTERIZATIONS OF CRACK GROWTH BEHAVIOR OF POROUS POLYMER MEMBRANES USING DIGITAL IMAGE CORRELATION AND FINITE ELEMENT METHOD

摘要

This study investigated the crack growth behavior of porous polymer membranes, experimentally and numerically, in order to clarify the criterion of crack growth. A notch was introduced into the membrane as an initial crack (pre-crack) and a uniaxial loading was applied for the stable crack propagation. During the test, crack propagation behavior was observed using a CCD camera and Digital Image Correlation (DIC) method. The strain around the pre-crack tip at the onset of crack propagation was measured experimentally using DIC method. It was clarified that large-scale yielding developed before the onset of crack growth. The stable crack propagation was observed for all tensile tests. In parallel, a homogenized model that mimicked porous polymer membrane was created using finite element method (FEM) in order to investigate stress/strain distribution around the crack tip. This study employed the yield criterion proposed by Deshpande and Fleck. The computed strain distribution was compared with that of experiment, showing a good agreement each other. By using strain distribution from DIC method and FEM computation, J-integral value was calculated to investigate the criterion of crack growth. Regardless of the initial crack length, it is found that the J-integral value at the initiation of crack growth becomes constant for all tests. It is concluded that we successfully determined the criterion of crack propagation of porous polymer membrane. Therefore, our study using DIC experiment and FEM computation is useful to clarify the crack growth behavior of porous polymer membrane and determines the criterion of crack propagation.