Force coefficient prediction for drilling of UD-CFRP based on FEM simulation of orthogonal cutting

This paper presents a mechanistic model for prediction of fluctuating thrust force and torque during drilling of unidirectional carbon fiber-reinforced polymer (UD-CFRP). A micro-scale model consisting of fiber, matrix, and fiber-matrix interface is proposed to simulate the orthogonal cutting behavior for the entire range of fiber orientation. Based on the FE model, a detailed energy analysis is conducted to quantify the various energy-absorbing mechanisms. The relationship between the percentage of each mechanism and factors such as depth of cut, tool rake angle, and fiber orientation is revealed. Afterwards, force coefficients related to these factors are obtained based on the orthogonal cutting database and used to calculate the instantaneous thrust forces and torque generated on the cutting lips, which are divided into a continuous set of infinitesimal elements conducting orthogonal cutting. Orthogonal cutting and drilling experiments with various machining parameters have been performed to validate the proposed FE and mechanistic models. Good correlation between the experimental and predicted results is found and thus the model is capable of predicting the fluctuation of thrust forces and torque for the whole drilling process.