Prediction of Fracture Energy and Flaw Size in Glasses from Measurements of Mirror Size

Fracture strengths (δ), fracture-initiating flaw sizes, and mirror radii ( r ), as outlined by either the mist or the hackle boundary, were measured for silicate and nonsilicate glasses (e.g. As₂S₃ and glassy carbon). For all glasses, δr^1/2= constant. The average ratios of inner and outer mirror radii to flaw size were ∼10:1 and ∼13:1, respectively, for most of the glasses. Critical fracture energies calculated from either flaw or mirror size agreed very well with those obtained by double-cantilever-beam measurements.