Size effect of depth of cut on chip formation mechanism in machining of CFRP

This paper investigates the effect of depth of cut on chip formation mechanism in machining of CFRP by the orthogonal cutting method. Characteristics of the cutting forces and the specific energy for material's removal under different depths of cut for different cutting angles are studied. Meanwhile, tool-material interactions are discussed for the effect on the failure mechanism combined with the on-line micro observation of the chipping process. Chip formation is the debonding-bending for 0°, and is the cutting-shearing for 45°. It is the buckling-dominant when the depth of cut is close to the cutting edge radius. Once the depth of cut is much larger than the cutting edge radius, the kinkband-shearing occurs for 90°, and the bending-dominant for 120°. Especially, the effect of the contact between the fiber and the cutting edge is analyzed based on the contact theory. It reveals fibers with strong constraint fracture at local contact area like 45°. However, it becomes a combination of the bending and the local contact due to the large bending deformation with the decrease of the off-axis modulus along the cutting direction like 90°. Furthermore, the bending-dominant chip formation easily results into the severe subsurface damage due to the large bending deformation.