The impacts of thermoelastic anisotropy and grain boundary misorientation on microcracking in ceramics

This paper examines the role of thermoelastic anisotropy on grain boundary cracking in brittle materials using a highly efficient computational framework. Energy release rates (ERRs) are computed for 35 materials spanning all seven crystal systems. Two crack geometries are considered: short interface cracks in isolated bicrystal plates, and cracked grain boundaries in polycrystal plates comprising periodic hexagonal grains. Crack driving forces are computed for penetration through the plate thickness (for cracks of width equal to the length of a hexagonal grain boundary), extension along bicrystal interfaces, transgranular cracks that emerge from triple junctions, and kinking into bulk materials and at grain triple junctions. The high throughput computational framework produces probability distributions for ERRs arising from randomly oriented grains; the distributions for cracks at grain edges in polycrystals are broader than those for short cracks along bicrystal interfaces. A broad study of different grain configurations also illustrates that only the first 5-6 rings of neighboring grains influence crack driving forces for a given interface. The implications for interpreting microcracking observations, quantifying the performance of textured ceramics, and designing two-phase ceramic composites are briefly discussed.