Strain inhomogeneity and discontinuous crack growth in a particulate composite

A full field method for visualizing strain fields around a crack tip under large strains is developed. Digital image correlation is used to compute st rains and displacements incrementally between consecutive images in a proce ss of large deformations. Values of strain and displacements for these cons ecutive deformations are added such that convergence of the DIC algorithm i s assured. The method is used to investigate the strain distribution in a g lobally homogeneously strained particulate composite (solid propellant) as well as in a zone close to (similar to 2 mm) the crack tip in such a materi al by using a microscope. It is found that maximal strain variations deviat e by as much as a factor of three from the average strain; additionally, ob servations on the interaction of strain inhomogeneities with the tip of a m acroscopic crack are discussed. (C) 1998 Elsevier Science Ltd. All rights r eserved.