Study Of Interlaminar Fracture Properties Of Ceramic Matrix Composites At Room And Elevated Temperatures

Interlaminar fracture properties play an important role in predicting failure of structural components for CMC materials. In engine applications, components are subject to large thermal gradients which induce interlaminar stresses. One of the main challenges in evaluating interlaminar fracture toughness at room and elevated temperatures is the development of an experimental setup that provides ease for testing and allows for in-situ monitoring of the interlaminar crack growth. Therefore, a wedge-loaded DCB testing method is developed. The method utilize electrical resistance to monitor crack growth and was applied to a woven polymer infiltrated pyrolysis (PIP) SiC/SiNC composite. Post-testing inspection was carried out using optical microscopy of polished cross-sections, showing crack morphology. It was found that crack growth rate at room temperature is double the one at 815 degrees C for initial tests in this composite system. Estimates of Mode I energy release rate suggests flat R-curve behavior at room temperature in comparison to rising R-curve behavior at 815 degrees C.