Abstract

Dynamic fragmentation processes are observed in brittle materials such as ceramics, concrete, glass or rocks submitted to impact loading or blasting. Under such loadings, tensile stresses at high stress-rate develop in the structure. This phenomenon generates a multiple fragmentation characterised by a high density of oriented cracks. The damage properties (namely, activated flaws, kinetics of damage and cracking density) as well as the dynamic strength of the material are important points to be understood.

In the present work, a micro-mechanical model is developed based on two concepts: the “local weakest-link hypothesis” and the “non-obscuration probability of an elementary space-time domain”. This model allows describing how the brittle probabilistic behaviour under quasi-static loading is changed into a determistic stress-rate-dependent behaviour with the increase of the loading rate. The nature of the fragmentation regime (i.e., single at low stress-rate and multiple at high stress-rate) is controlled on the one hand by the volume size of the structure and on the other hand by the loading rate. This model is used to predict the damage properties of several kinds of brittle materials during impact tests.