Study on the formation mechanism of cutting surface of carbon fiber-reinforced composites

Carbon fiber-reinforced plastic (CFRP) is used widely in aerospace. The cutting mechanism of CFRP is markedly different from that of metals due to anisotropic and non-homogeneous material structure. The cutting mechanisms are highly dependent on the fiber orientation. The quality of the machined surface can be affected by the fiber fracture models. In this paper, based on the elastic foundation beam theory and the Hertzian contact theory, the cutting mechanics are established. And the cutting model is simulated by the three-dimensional micro-scale numerical model. Then, the continuous varying cutting mechanism and the sub-damage are deeply studied in detail by combining the cutting mechanics model and the simulation model. The results indicate that the fiber orientation θ = 80° and θ = 150° is the transition critical point of the fracture form. When θ = 0°, the fiber failure mode is buckling dominated. When 0° < θ < 80° and 150° < θ < 180°, the fiber failure mode is dominated by contact fracture. When 80° < θ < 150°, the fiber failure mode is bending-dominated. The cutting mechanics model and finite element model can effectively reflect the evolution law of CFRP-machined surface.