The edge cracking and spalling of brittle plates

The cracking and spalling processes that accompany the edge loading of brittle plates have been investigated. Experiments performed on glass and on PMMA have revealed systematic trends in crack location, crack propagation load, and in the onset of spalling. In particular, a steady state crack growth region has been identified wherein the cracks propagate parallel to the side surface. Calculations of mode I and mode II stress intensities have allowed comparison of the crack trajectories and crack propagation loads with experimental measurements. The general trends in cracking were found to be broadly consistent with predicted behavior governed by a zero mode II criterion and assuming that the cracks grow into a steady state trajectory. However, some quantitative discrepancies exist. These have been attributed to constraining tractions that develop upon distortion of the test specimens.