Propagation of tensile planar cracks in highly heterogeneous media: A numerical study

Effect of highly heterogeneous fracture properties on tensile penny-shape planar crack propagation governed by Irwin's criterion is investigated numerically by taking into account the large crack front deformations induced by the high toughness contrasts. To compute the variations of stress intensity factor (SIF) along the crack front arising from its progressive deformation, perturbation approach based on Bueckner-Rice weight function theory is used iteratively. Effective fracture toughness is obtained from the local toughness map for a few examples. It is shown that when Irwin's criterion is satisfied all along the crack front, the effective toughness is equal to the mean value of the local ones along the crack front. This value depends on the shape of the front, and so is different from the total mean value of the toughness in the plane. In the examples studied here, the weak toughness zones are favored by the crack front deformations, so that the effective toughness is lower than its spatial average.