Prediction of Fracture and Detection of Fatigue in Ceramic Composites from Electrical Resistivity Measurements

Fracture prediction and fatigue detection techniques in ceramic composites were examined. Composites with an electric conduction path were fabricated with ceramics having different electrical resistivity, using calcium fluoride powder as the insulating matrix and silicon carbide whiskers as the conducting additive. When a bending load was applied to the test piece, the electrical resistivity of the composites increased up to fracture. When the test pieces were repeatedly loaded below the fracture limit, there was a gradual increase of electrical resistivity before fracture. These phenomena suggested the possibility of predicting fracture and detecting fatigue in ceramic composites. The movement of whiskers disconnecting the conduction path and leading to an increase in electrical resistivity was confirmed by scanning electron microscopy observation.