Fracture criterion for glass under impact loading

Resistance to impact of brittle materials has been the subject of many recent studies. Glass material with its various applications is very sensitive to impact loading. Under impact conditions where stress waves and their interactions are dominant, failure may be initiated simultaneously at some sites. The stress distribution varies rapidly with time and position. This study, based on previous works on cumulative damage models, concerns a glass plate subjected to impact at different loading rates using two methods: a compression split Hopkinson pressure bar and the normalized drop ball test. In order to evaluate the damage development and the fragmentation, we propose a damage model characterized by the damage volume affected by impact. This volume is a function of impact duration and critical stress. Damage rate is therefore predicted by the severity of a dynamic contact between the projectile and the target. Indeed, the multi-activation of micro-defects depends on this volume. Perforation of the glass plate occurs at a level of stress close to ten times the tensile strength.