Calibration and Validation of a Material Point Method Ceramic Damage Model for Split-Hopkinson Pressure Bar Simulations

In this work, we consider the direct numerical simulation of the uniaxial compression of 5mm diameter composite samples of idoxuridine (idox) in a nitro-plasticized estane binder (idox-estane) at high strain rates. We present the process including calibration of the constituent materials, difficulties and considerations of the full sample simulation, and validation efforts.

Inert surrogates, commonly referred to as ``mocks,'' such as idox, are often used in place of high explosives due to clear safety and handling concerns. Like their energetic counterparts, these mocks are typically brittle and are chosen to approximate the thermo-mechanical response of their energetic counterparts across a wide range of loading rates. Brittle and quasi-brittle materials are known to degrade primarily through the formation and growth of microcracks, the development of macro-scale cracks, and the eventual coalescence of these cracks, leading to fracture and fragmentation. The difficulties associated with the numerical simulation of fracture and fragmentation in single crystals are only further confounded when considering the full idox-estane composite samples. By choosing to use the material point method (MPM) with statistically variable size-dependent strength scaling, gradient-field partitioning, and a ceramic damage material model for the embedded idox crystals, we address challenges related to regularization, post-failure dynamics, accuracy, and robustness in material characterization.