An energy condition for initiation of interfacial microcracks at inclusions

Fracture mechanics is applied to the problem of microcrack initiation on cylindrical (spherical) particles in a matrix. The numerical calculations have been performed by the finite element method.A stress criterion for the initiation of interfacial, cap shaped, microcracks is derived as function of inclusion size and bonding strength. It is found that the cracks are unstable below a minimum “cap angle”. Comparison with experiments shows reasonable quantitative agreement.