Crack length dependence of mode III delamination using edge crack torsion test

Abstract

The objective of this study is to compare the mode III delamination behavior of edge crack torsion (ECT) specimens at different initial crack lengths, ao. Finite element models of ECT specimens at ao = 20 mm and 30 mm were developed based on the data from the literature. Delamination behavior was investigated using cohesive zone modeling, where cohesive elements were placed at the mid-thickness of the specimens. Results showed that the experimental and numerical force-displacement curves were comparable, with less than 10% difference in the slopes and peak loads. In addition, it was found that the cohesive zone in both models contained three elements. Furthermore, the crack front (CF) and fracture process zone (FPZ) contours revealed that the largest crack extensions were found at normalized locations of approximately 0.4 and 0.7 for ao = 20 mm and 30 mm specimens, respectively. Finally, comparison between the fracture energy distributions and phase angle indicated that at least 30% of the crack front was mode III dominant, with phase angle of 85° and above.