A multi-mechanism based constitutive model is presented for brittle ceramics subjected to projectile impact loading. The mechanisms considered as part of this model includes multi-scale fracture, an equation of state, granular flow, amorphization and pore-evolution. The multi-scale fracture is represented at the macroscale through an isotropic damage parameter; the evolution of which is governed by micromechanics principles of an ellipsoidal inclusion at the mesoscale. This mesoscale description of an ellipsoidal inclusion is related to a wing crack model to describe dynamic crack propagation at the microscale. The equation of state defines the evolution of volumetric part of the deformation tensor with pressure and temperature. At a certain level of damage, it is assumed that the material loses coherency and granular particles formed eventually flows. The granular flow mechanism has been accounted using a plasticity model. In granular flow, pore spaces are also evolved so thereby the plasticity model is capped based upon a pore-evolution model. Apart from these mechanisms, another mechanism typically observed in certain ceramics (such as Boron carbide): amorphization has also been modeled. The amorphization model is based upon a set of rules defining the onset, evolution and sliding along amorphization bands.
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