Effects of Composition and Environment on the Fracture of Fluoride Glasses

Indentation‐crack‐length procedures were used to determine the critical fracture toughness (KIC) and the sensitivity to environmentally enhanced crack growth in heavy‐metal fluoride glasses of varying chemical composition. The data show that while KIC was more or less invariant with composition, some glasses were more susceptible to subcritical crack growth than others. The results are interpreted in terms of existing crack‐growth models. A technique for predicting KIC from fundamental atomic bonding and crystal‐structure data for these glasses is discussed.