Comparative study of static and cyclic fatigue of ZrB2-SiC ceramic composites

Room temperature static and cyclic fatigue of ZrB2-32 vol% SiC and ZrB2-45 vol% SiC particulate ceramic composites has been studied. It was established that the presence of grain bridging plays an important role in the lifetime and time dependent mechanical performance of ZrB2-SiC composites. It was also established that the cohesive strength of grain boundaries of the composites was a determining factor if grain bridging would occur during crack growth, as the grain boundaries strength would determine the pathway of the moving crack. Grain bridging was limited in ZrB2-32 vol% SiC leading to the absence of a cyclic fatigue effect, while grain bridging indeed occurred in ZrB2-45 vol%SiC contributing to a cyclic fatigue effect which limits the lifetime of the composite. Such differences were responsible for the occurrence of R-curve behavior in ZrB2-SiC ceramic composites.