Force prediction in milling of carbon fiber reinforced polymers

Fiber reinforced polymers are widely used in the transportation, aerospace and chemical industries. In rare instances these materials are produced net-shape, and secondary processing such as machining and assembly may be required to produce a finished product. Because fiber reinforced polymers are heterogeneous materials, they do not machine in a similar way to metals. Thus, the theory of metal machining is not valid for the analysis of machining of fiber reinforced composites. Previous attempts in modeling this problem have adopted Merchant's theory for metal cutting by assuming that chip formation takes place in a shear plane where the inclination angle is determined by the minimum energy principle. This class of models showed that model predictions are valid only for fiber orientations less than 60 degrees. Furthermore, these models are incapable of predicting cutting forces for multidirectional laminates or complex tool geometry. The work presented here focuses on providing a predictive model for the cutting forces in milling both unidirectional and multidirectional laminates. The model is based on the specific cutting energy principle and accounts for a wide range of fiber orientations and chip thickness. Results from this model were found to be in good agreement with experimental results over the entire range of fiber orientations from 0 to 180 degrees.