FRACTURE AND DEFECT ASSESSMENT OF CERAMIC COMPOSITES

— Industrial ceramic crucibles manufactured by hot-pressing a mixture of ceramic powders sometimes fail by delamination when operated under extreme conditions. Results of laboratory tests under similar conditions suggest that failure may be caused by the constrained evaporation of a water rich liquid absorbed by relative large aggregate particles. Fracture mechanics test results, from specimens cut parallel and transverse to the direction of hot pressing, revealed a clear anisotropic behaviour and a large sensitivity to notch size for notches smaller than a millimetre in depth. A model based on the existence of a notch-tip damage zone is proposed and used to present fracture curves that can be employed for failure assessment of industrial crucibles.