The interaction between the cutting force and induced sub-surface damage in machining of carbon fiber-reinforced plastics

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 degrees to 135 degrees. Fiber orientation is the critical factor affecting the cutting force and the sub-surface damage. More subsurface damage occurs in a fiber orientation range of 90-135 degrees. 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.