Prediction of crack nucleation and propagation in porous ceramics using the phase-field approach

The relevance of the phase-field approach to simulate the fracture in porous ceramics has been investigated. For this purpose, the conditions for the crack initiation using the phase-field model have been compared to the theoretical predictions of the coupled criterion considering a pure V-notch singularity and a crack blunted by a cavity. For two types of ceramics (3YSZ and 8YSZ), it has been shown that the phase-field approach is able to simulate accurately the crack nucleation as predicted by the coupled stress-energy criterion. The nature of the regularization parameter l for the phase-field model has been discussed as function of the material and the local geometry where the crack initiates. Moreover, the apparent fracture toughness and the compressive fracture strength have been calculated for real porous YSZ ceramics. It has been found that the fracture properties of these complex 3D porous materials can be correctly predicted with the phase-field model. For specimen loaded under compression, it has been shown that the model is able to capture and explain the transition from a brittle behavior towards a diffuse damage when increasing the porosity.