Microstructural mechanisms for enhancing energy dissipation and spall resistance in SiC

Abstract

Key microstructural features such as grain size, grain shape, crystallographic orientations, and grain boundary properties strongly influence fracture resistance of ceramics. Well-designed microstructural features contribute to the materials’ ability to withstand dynamic loading and deformation by facilitating mechanisms that dissipate energy and prevent catastrophic failure. In this research, a microstructure-explicit and fracture process-explicit computational framework is employed to better understand how these microstructural features impact the dynamic fracture response of SiC during high-rate compression loading and spallation. Utilizing the cohesive finite element method (CFEM), the model incorporates anisotropic bulk constitutive and fracture behaviors of grains and misorientation angle-dependent grain boundary properties to resolve complex crack paths and fracture patterns. The model also captures the effects of intergranular and transgranular fracture, and friction between crack faces. A key observation is that grain size gradient can be utilized to balance and optimize both compressional energy dissipation and spall strength. Additionally, it was shown that the effect of crystallographic texture on spall strength is strongly dependent on both the volume fraction and orientation of preferentially aligned grains. Lastly, the study finds that the anisotropic fracture behavior of the grain boundary has a more pronounced effect on both spall strength and energy dissipation than the degree to which anisotropy changes as a function of misorientation angle. The findings provide insight into microstructural features that optimize energy dissipation and spall strength under specific loading conditions. Furthermore, the model framework can be extended to guide the microstructural design of other ceramics and ceramic composites.