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Flaw distributions, subscale crack interactions, and dynamic failure of ceramics

Andrew Tonge (The Johns Hopkins University), K.T. Ramesh (Johns Hopkins University)

Dynamic Behavior of Materials

Tue 9:00 - 10:30

Salomon 101

Failure in armor ceramics, like failure in other brittle materials is the result of the activation, interaction, and finally the coalescence of flaws within the material. At low rates the timescale associated with the material loading rate is much larger than the communication time between flaws. As a result, the failure tends to be dominated by the largest flaws in the system. At higher rates the dynamics of crack growth become important, because they place an upper bound on the rate that any single crack can dissipate energy. This dynamic effect causes other, smaller and more numerous flaws to become active in the failure process. We capture the interaction and dynamics of the sub-scale flaw population using a micromechanics based damage model. The explicit simulation of an evolving subscale crack population allows us to incorporate the macroscopic variability that is observed experimentally using a natural approach based on a simple sampling approach. In this work we discuss the point-to-point variability introduced by the sampling process and how that interacts with the subscale crack dynamics and the macroscopic loading conditions leading to failure in a model ceramic in confined dynamic compression tests.