Delamination vs matrix cracking in layered composites subjected to transverse loading

An algorithm is presented to compute the distribution of the strain energy release rate along the crack front of a penny-shaped delamination in a layered orthotropic body. The method applies a finite element recently proposed for three-dimensional analysis of layered orthotropic circular plates. The algorithm is economical even though it treats a full three-dimensional state of stress. The method requires only a single virtual crack extension to accurately compute the strain energy release rate at a point along the crack front. The method is applied to the study of delamination crack growth in a nine layer cross-ply laminate. The variation of strain energy release rate, G, along the crack front, is determined. The significance of the plate aspect ratio, as well as length scale, on the fracture process is studied. The establishment of a loading case where a distributed transverse compressive loading causes delamination growth is given.