A multi-mechanism constitutive model for the dynamic failure of quasi-brittle materials. Part I: Amorphization as a failure mode

This is the first part of a 2-paper series describing a generalized multi-mechanism constitutive model for the dynamic failure of quasi-brittle materials (e.g., ceramics and geomaterials), and focus on the poorly understood mechanism of amorphization. Amorphization has long been recognized as a significant deformation mechanism in a variety of quasi-brittle materials. In this part, we develop an amorphization model based on observations in both experiments and atomistic simulations. We consider the onset of amorphization bands and the deformation of amorphous phases inside the bands. The sliding along amorphization bands introduces damage to the materials, which eventually results in material failure, and the response of the failed material is described as granular flow. Using boron carbide (BC) as a representative material, we determine the material parameters and validate the model using plate impact experiments under different shock conditions. Finally, we use the model to predict the response of BC under dynamic Vickers indentation, and compare the simulation results with experiments from the literature to demonstrate the capability of the proposed model.