FRACTURE-MECHANICS OF FUNCTIONALLY GRADED MATERIALS

In this paper, after a brief discussion of the elementary concepts of fracture mechanics in nonhomogeneous materials, a number of typical pr oblem areas relating to the fracture of functionally gradient material s (FGMs) are identified. The main topics considered are the investigat ion of the nature of stress singularity near the tip of a crack fully embedded in a nonhomogeneous medium, the general problem of debonding of an FGM coating from a homogeneous substrate, the basic surface crac k problem in FGMs and cracking perpendicular to the interfaces, period ic surface cracking and the associated problem of stress and energy re laxation, and the problem of stress concentration at and the initiatio n and growth of delamination cracks from the stress-free ends of FGM-c oated homogeneous substrates under residual or thermal stresses. Each topic is very briefly reviewed, some sample results are presented and comparisons with the corresponding results obtained from homogeneous m aterials are made.