Carbon fiber-reinforced plastics (CFRPs) have the characteristics of non-homogeneity and anisotropy. Damage occurs frequently in machining of CFRPs, and it can seriously influence the performance of work piece. This study builds a finite element model for machining of CFRPs based on the constitutive relation with damage, the Hashin failure criterion, and the damage evolution. The continuous cutting processes of unidirectional CFRPs with various fiber orientations are simulated. Cutting forces and sub-surface damage are determined from simulations. Furthermore, machining experiments on unidirectional-CFRPs are performed. Cutting processes are monitored, and cutting forces are measured. An artificial neural network (ANN) force model is proposed by using the experimental data, and then simulation results of the cutting forces are validated by these of the ANN model. Cutting force increases when the fiber orientation varies from 0° to 135°. Fiber orientation is the critical factor affecting the cutting force and the sub-surface damage. More sub-surface damage occurs in a fiber orientation range of 90–135°. The primary reasons for the induced sub-surface damage include the damage evolution and the crack propagation of matrix caused by the cutting force. In addition, the effects of cutting parameters and tool geometries on the cutting force and the damage are discussed by simulations. The cutting force thus can be reasonably controlled to reduce the damage.

The essence of cutting carbon fibre-reinforced plastic (CFRP) composites is a process of material failure and chip formation. The mechanism of cutting CFRPs can be explained from the perspective of local removal of material on the microscopic level. The morphology of the chips resulting from the cutting process can be determined from the perspective of the overall failure of the material on the macroscopic level. To reveal the mechanism of cutting CFRPs at both levels, a macroscopic model and a microscopic model are established in this study. Orthogonal cutting is applied in both of the models to illuminate the removal process. Combined with experimental observations, the results that obtained from both the macroscopic and microscopic level revealed the different mechanics of cutting CFRPs for different fibre orientations. For example, the forms of fracture that occur at 0° fibre orientation are primary interface cracking and fibre bending; the resulting chips have long shapes.