Fracture mechanical analysis of open cell ceramic foams under multi-axial mechanical loading

Ceramic foams made by replica techniques contain sharp edged cavities, which are potential crack initiators. This paper presents an approach to analyse such structures with respect to their fracture mechanical properties. A fundamental domain of an open cell Kelvin foam is used to model the geometry including the cavities and to generate a finite element model of the structure. Sub-models containing crack tip elements are used to resolve the local stress fields at the vicinity of the sharp-edged cavities. The interaction integral is used to compute the local stress intensity factors under multi-axial loading. Using a homogenization approach, a criterion for brittle failure based on the effective stress state is presented. The failure criteria can be extended to account for the anisotropic behaviour of the foam structure.