Comparison Of Methods To Determine The Fracture Toughness Of Three Glass-Ceramics At Elevated Temperatures

Two standardized methods for measuring KIc in ceramics are compared for use at high temperatures (precracked beam and surface crack in flexure). Results from a third technique involving the measurement of cracks around Vickers indentations are also presented. Three dental glass-ceramics, differing primarily in microstructure, were used as model materials in this study. They emphasized the importance of microstructure in determining high-temperature KIc values and the challenges in measuring them. The measured fracture toughness decreased with temperature and increased with imbedded grain size for all three methods.