PREDICTION OF CRACK DEFLECTION AND KINKING IN CERAMIC LAMINATES

摘要

The arrangement of ceramic layers in laminated structures is an interesting way to enhance the flaw tolerance of brittle ceramic materials. The interfaces are expected to deflect cracks, increasing the fracture energy of the laminate compared to a monolithic material and thus raising the toughness. The crack deflection has been studied in a previous paper, the analysis focuses now on the crack kinking out of the interface. The criterion for kinking prediction relies on a two-scale analysis taking into account the laminated structure of the material. It can be written in terms of a single material parameter: the volume fraction of pores. Crack deflection is promoted only for very high values of the porosity. Predicted values agree satisfactorily with experiments. This porosity is generally high enough to ensure that the crack remains within the interface after deflection without kinking out. Then, the final ruin of the structure can occur only by successive onsets of new cracks.