Comparison of Methods to Determine the Fracture Toughness of Three Glass‐Ceramics at Elevated Temperatures

Abstract

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 toughnesses decreased with temperature and increased with imbedded grain size for all three methods.