Abstract
The crack initiation at the sharp edges of dispersed inclusions plays an important role in the strength of dispersion composite materials. This paper discusses the crack initiation at the tips of a flat inclusion from the viewpoint of energy release rate. On the basis of the two-dimensional theory of elasticity, numerical calculations are carried out for the energy release rate for the crack initiation. The maximum energy release rate and its direction for Poisson's ratio of matrices are figured. The tension and equivalent compression tests are performed by using epoxy resin specimens containing a flat steel inclusion. The theoretical result for the direction of the maximum energy release rate is compared with the observed crack initiation angle. Both results coincide fairly for tension tests, while they do not coincide for compression tests.
