We describe models for the behavior of hot-pressed boron carbide that is subjected to extreme dynamic environments such as ballistic impact. We first identify the deformation and failure mechanisms that are observed in boron carbide under such conditions, and then review physics-based models for each of these mechanisms and the integration of these models into a single physics-based continuum model for the material. Atomistic modeling relates the composition and stoichiometry to the amorphization threshold, while mesoscale

A micromechanical multi-physics model for ceramics has been recalibrated and used to simulate impact experiments with boron carbide in ABAQUS. The dominant physical mechanisms in boron carbide have been identified and simulated in the framework of an integrated constitutive model that combines crack growth, amorphization and granular flow. The integrative model is able to accurately reproduce some of the key cracking patterns of Sphere Indentation experiments and Edge On Impact experiments. Based on this integrative model, linear regression has been used to study the sensitivity of sphere indentation model predictions to the input parameters. The sensitivities are connected to physical mechanisms, and trends in model outputs have been intuitively explored. These results help suggest material modifications that might improve material performance, prioritize calibration experiments for materials-by-design iterations, and identify model parameters that require more in-depth understanding.

The paper presents a numerical model to study the transition of brittle materials from a cracked solid to a granular medium under impact loading. The model addresses competitive crack coalescence in the transition regime and provides insight into the onset of comminution and the initial conditions for subsequent granular flow. Crack statistics obtained from initial flaws using a wing crack growth-based damage model have been used to discretely model elliptical cracks in three dimensions. These discrete cracks are either generated randomly in space or with a constraint that minimizes the intersection between neighboring cracks. These cracks are then allowed to coalesce with nearby cracks along with favorable directions and the output fragment statistics are predicted. A simple statistical model is proposed that suggests a transition criterion resembling the one obtained from the numerical model. Initial fragments are power-law distributed similarly to experimental observations and particle-based models. A generalized form of a microstructure-dependent granular transition criterion based on a threshold measure of crack lengths has been proposed. This model can be implemented in numerical codes to activate granular physics and calibrate the initial conditions of granular flow, such as fragment size and morphology.

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