On Terminal Crack Velocities In Glasses

A review of the literature shows that terminal crack velocity should be correlated with the longitudinal elastic wave velocity, and the structure and density of glasses. Theoretical predictions of Vct by the Mott-Roberts-Wells model match experimental measurements for some key glasses, including fused silica and low density borosilicates. It is suggested that the slower Vct results obtained for many other glasses are due to structural variations that cause crack front perturbations. The conclusions of this paper are most likely applicable to ceramics as well.