Transition of material removal mechanism in cutting of unidirectional SiC_f/SiC composites

SiC_f/SiC composites are difficult-to-machine materials with high hardness, high brittleness, and anisotropy. Exploring the material removal mechanism in depth is the key basic research to achieve high-quality machining of ceramic matrix composites. The results of orthogonal cutting experiments indicated that the brittle regime of ceramic matrix composites during cutting could be further subdivided into micro brittle fracture regime and macro brittle fracture regime, based on the different basic material units where fiber brittle fracture occurs. A critical cutting depth model for micro–macro brittle fracture transition of ceramic matrix composites was established based on orthogonal cutting theory and composite micromechanics. Comparison of experimental results and model calculation results indicated that the critical cutting depth model for micro–macro brittle fracture transition had high reliability. The critical cutting depth of micro–macro brittle fracture transition in the cutting of SiC_f/SiC composites was less than 12 μm.