Mixed-Mode Fracture in Soda-Lime Glass

Soda-lime-silica glass was fractured under combined mode I and mode II loading from flaws produced by hardness indentations. Critical stress intensities calculated from K₁ and K₁₁ combined using four analyses, are compared to K_IC measured by a fracture mechanics technique and to values of K_IC determined by measuring fracture-mirror size. The comparison showed that K_IC calculated using a noncoplanar strain-energy release-rate analysis gave the best agreement with values obtained by fracture mechanics techniques over the widest range of crack orientations. K_ICcalculated from mirror sizes was constant regardless of the orientation of the original flaw.