Crack propagation and fracture resistance behavior under fatigue loading of a ceramic matrix composite

The crack growth behavior of unidirectional silicon carbide (SCS-6) fiber reinforced zircon (ZrSiO4) matrix composites under cyclic fatigue is studied in the temperature range 20-1400degreesC. In situ crack length measurements under fatigue loading are obtained from single edge notched specimen using a traveling optical microscope. Fracture resistance curves (R-curve) are obtained from the experimental crack growth data, which show a rising R-curve behavior with a decreasing value of the fracture resistance at elevated temperatures. Numerical analyses/iterations, based on the micromechanical models, are done to determine the relationship between the bridging stress function and the R - curve behavior of the composite. The effect of residual stress and constituent properties such as fiber strength, interfacial shear stress, and matrix toughness on the bridging stress function is systematically studied both at room and elevated temperatures.