Grinding defect characteristics and removal mechanism of unidirectional Cf/SiC composites

Owing to their brittleness and heterogeneity, achieving carbon fiber-reinforced silicon carbide ceramic (C_f/SiC) composites with ideal dimensional and shape accuracy is difficult. In this study, unidirectional C_f materials were subjected to orthogonal grinding experiments using different fiber orientations. Through a combined analysis of the surface morphology and grinding force after processing, the mechanism underlying the effect of the fiber orientation on the surface morphology of the material was explained. The surface roughness of the material was less affected by the process parameters and fluctuated around the fiber radius scale; the average surface roughness (R_a) in the direction of scratching parallel (SA) and perpendicular (SB) to the fiber direction was 4.21‒5.00 μm and 4.42‒5.26 μm, respectively; the material was mainly removed via the brittle removal mechanism; and the main defects of the fiber in the SA direction were tensile fracture and extrusion fracture; the main defects of the fiber in the SB direction were bending fracture, shear fracture, and fiber debonding. The grinding parameters influenced the grinding force in the order: depth of cut > feed rate > wheel speed. The grinding force increased with an increase in the feed rate or depth of cut and decreased with an increase in the wheel speed. Moreover, increasing the depth of cut was more effective in decreasing the grinding force and improving the material removal efficiency than adjusting the rotational speed of the workpiece and the rotational speed of the grinding wheel. The specific grinding energy decreased with an increase in the feed rate or depth of cut, and increased with an increase in the grinding wheel speed.