Effect of cutting tool geometry on material removal in orthogonal cutting of unidirectional Cf/SiC composites: A fracture-energy-based interpretation

Machining carbon fiber reinforced silicon carbide (Cf/SiC) composites is associated with high cutting forces, surface damage, and rapid tool wear due to their brittle and anisotropic nature. A clear understanding of fracture-controlled material removal is therefore essential for improving machining performance. This study investigates the influence of tool geometry on the orthogonal cutting behavior of unidirectional Cf/SiC composites. Synchronous image–force acquisition is employed to directly capture chip formation, while post-machining surface characterization provides complementary evidence of fracture evolution. As expected, the results indicate that material removal is predominantly governed by crack initiation and propagation rather than continuous plastic shear deformation. At a 0° fiber orientation, decreasing the rake angle induces a transition from bending-dominated (Mode I) fracture to compression-induced shear (Mode II) fracture. At 45° and 90°, removal is mainly controlled by transverse fiber shear fracture and interfacial sliding, whereas at 135° bending-related fracture becomes more significant under compressive conditions. Clearance angle and tool edge radius primarily modify local contact stresses but do not fundamentally alter the fracture-dominated removal mechanism. Based on these observations, a fracture-energy-based framework is established to interpret how tool geometry and fiber orientation influence stress state, fracture mode selection, and energy dissipation during cutting. The framework provides qualitative consistency with experimentally observed force trends and offers a unified physical interpretation of fracture-controlled machining in Cf/SiC composites. This work enhances mechanistic understanding of brittle composite cutting and contributes to the development of tool design strategies for controlled, low-damage machining.