A multi-mechanism constitutive model for the dynamic failure of quasi-brittle materials. Part II: Integrative model

In Part I, we established a model for amorphization during the failure of quasi-brittle materials. In this Part II, we present a multi-mechanism physics-based constitutive model which incorporates amorphization, microcracking and granular flow as basic deformation mechanisms. With this new integrative model, we investigate the interaction and competition of the different mechanisms. In the amorphization model we considered the initiation and evolution of amorphization bands. Microcracking is described with the micromechanics-based damage model developed in Tonge and Ramesh (2016a). Both amorphization and microcracking may introduce damage to the material, and granular flow is activated when the accumulated damage reaches some threshold value. Using boron carbide (BC) as the model material, we examine the response of a representative volume element (RVE) under different loading conditions and loading rates. We apply the full model to full simulations of plate impact and dynamic Vickers indentation into the material. Next, we simulate the sphere-on-cylinder impact experiments as an application of the integrative model. By comparing the simulation results with experiments and studying the influence of the various material parameters, we demonstrate the ability of the integrative model to capture the effects of multiple mechanisms and suggest some promising directions for material-design.