Impact failure modes in glass structures

Abstract: A range of glass-based structures of various constructions and thicknesses have been subjected to impact loading by stone chippings similar to those found on the roadside. The failure modes have been examined in an attempt to elucidate the failure mechanisms and processes in these systems. Initial tests generated radial and lateral cracking at velocities well above that required to initiate damage; this form of cracking was not observed again since attention was focused on the critical velocity for damage initiation. Thinner structures were found to fail primarily by star cracking, a flexure induced rear surface failure. Thicker structures generally failed by partial cone cracking, a contact induced front surface failure. The addition of a polymeric layer to the glass monolith had no effect on the failure mechanisms, while the addition of an inner layer of glass (yielding a laminated construction) had a secondary influence on the impact resistance of the structure. This was clearly apparent for intermediate outer glass thicknesses, where an increase in the inner glass thickness causes the stiffness of the panel to increase sufficiently to alter the failure mode and thus cause an increase in the critical velocity for damage initiation