Cracks in functionally graded materials

semi-infinite crack in a strip of an isotropic, functionally graded material under edge loading and in-plane deformation conditions is analyzed. Mixed mode stress intensity factors are analytically solved for up to a numerically determined parameter. The effects of material gradients on the mode I and mode II stress intensity factors and the phase angle used to measure mode mixity are determined. The solution is extended to the case where the strip is made of an orthotropic, functionally graded material. These results are applied to solve a four-point bending specimen configuration that may be used to test the fracture behavior of functionally graded materials. The nature of the crack tip fields and possible fracture criterion for functionally graded materials are discussed. Copyright 0 1996 Elsevier Science Ltd 1. INTRODUCTION