Fracture criterion for glass under impact loading

Resistance to impact of brittle materials has been the subject of many rece nt studies. Glass material with its various applications is very sensitive to impact loading. Under impact conditions where stress waves and their int eractions are dominant, failure may be initiated simultaneously at some sit es. The stress distribution varies rapidly with time and position. This stu dy, based on previous works on cumulative damage models, concerns a glass p late subjected to impact at different loading rates using two methods: a co mpression split Hopkinson pressure bar and the normalized drop ball test. I n order to evaluate the damage development and the fragmentation, we propos e a damage model characterized by the damage volume affected by impact. Thi s volume is a function of impact duration and critical stress. Damage rate is therefore predicted by the severity of a dynamic contact between the pro jectile and the target. Indeed, the multi-activation of micro-defects depen ds on this volume. Perforation of the glass plate occurs at a level of stre ss close to ten times the tensile strength. (C) 2001 Elsevier Science Ltd. All rights reserved.