Anisotropy effects on crack path formation at atomistic-continuum scales

Crystallographic and structural anisotropies are essential in governing the direction of crack propagation, particularly for brittle materials and their composites. However, capturing their combined effects and relative influence on crack-path formation at atomistic-continuum scales remains challenging. This paper presents a multiscale framework to determine the role of crystallographic anisotropy in controlling fracture in 3C-SiC and its composites. This framework decomposes the continuum media into a collection of "crystal-symmetry preserved sub-domains" (CSPS) before finite element discretization. Interactions and continuum scale behavior of the CSPS are described by continuum scale parameters determined from atomistic simulations. The framework reproduces all essential features of the atomic scale fracture, including bifurcation, arrest, renucleation, deflection, and penetration. Results reveal that "crystallographic anisotropy" controls the local anisotropy in the propagation pathway, whereas "structural anisotropy" controls the path deviation from the symmetry plane. The fracture pattern emerges from a competition between structural and crystallographic anisotropy effects and long-range elastic interactions among the stress-concentration sites. The underlying physics in high-symmetry configurations is well-explainable using "bifurcation diagrams."