Mechanisms of surface finishing during cutting of composite materials

An attempt has been made to explain the formation of pores on the finished surface of short-fiber-reinforced composite materials, which is brought about by fiber detachment during cutting. A stress analysis of the deformation and fracture behavior caused by the progress of the cutting edge in the macroscopic region at the interface between the matrix material and the fiber is carried out using an elastoplastic finite-element method. This analysis reveals that stress is concentrated at the interface between the matrix material and the fiber far from the cutting edge as a result of the contact of the cutting edge. It is also revealed that cutting occurs by continuance of the microscopic fracture mechanism involving interfacial fracture between the matrix material and fiber far from the cutting edge. Analysis of the fracture region shows that the pore depth is 0.5 which corresponds to the fiber diameter. This is in relatively good agreement with the experimental value of 0.3. Even before the cutting tool touches the fiber, tensile stress is generated in the fiber and it is likely to produce its fracture.