Overall moduli of solids with microcracks: Load-induced anisotropy

Abstract For a linearly elastic brittle solid containing microcracks that may be closed or may undergo frictional sliding, a general method is developed for estimating the overall instantaneous moduli which depend on the loading conditions. When the cracks are all open and when they are randomly distributed, then the overall response is isotropic. The moduli for this case have been obtained by B udiansky and O'C onnell (1976). On the other hand, when some cracks close, and when some closed cracks undergo frictional sliding, then the overall response becomes anisotropic and dependent on the loading conditions, as well as on the loading path. The self-consistent method is used to estimate the overall moduli. The effects of crack closure and loadinduced anisotropy are included. Several illustrative examples are worked out, showing the important influence of the load path on the overall response when crack closure and frictional sliding are involved.