Indentation-Induced Damage Initiation and Evolution in Single- and Poly-Crystalline Ceramics

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A joint experimental and modeling effort is proposed to study the initiation and growth of crack and the interplay between fracture and plasticity in single- and poly-crystalline ceramics. First, the validity of indentation-cracking method for toughness measurement will be examined, and a parametric map will be constructed to delineate the dependence of the ratio of crack size and contact radius on indenter geometry, applied load, toughness, and hardness. Second, by experimentally examining the behavior of several SiC materials during load and depth sensing spherical indentation tests and comparing it to microstructurally based finite element simulations based on crystal plasticity with coupled intergranular and transgranular microfracture using a cohesive zone approach, a detailed picture of the coupled deformation and micro-fracture processes will be developed from which it will be possible to make predictions about how to tailor a microstructure to optimize its energy absorption. The ability to quantitatively predict the initiation and propagation of fracture and the interaction between fracture and plasticity is a critical step towards a mechanistic understanding of deformation and failure properties, as well as ductility and toughness enhancement methods, of ceramic single crystals and polycrystals. The proposed work will provide an excellent opportunity for the graduate and undergraduate students to participate in an experimental/modeling synergistic research that includes micromechanics modeling and computation, and advanced mechanical testing and microstructural characterization. New educational materials will be developed and disseminated through two graduate level classes. The PIs will participate in the existing programs at their institute (supported by NSF and Department of Energy) for education/outreach activities, which are designed to inspire interests of high school and college students in science and engineering careers, as well as for recruiting students from underrepresented groups.