A numerical approach to analyze the burrs generated in the drilling of carbon fiber reinforced polymers (CFRPs)

Burrs generated in the drilling process of carbon fiber-reinforced polymers (CFRPs) can cause delamination, therefore significantly reduce the bearing capacity of the components during service. In order to address this issue, the multiscale finite element (FE) modeling was developed in this work to analyze the burrs formation mechanism. The proposed model combined the microscopic fiber and matrix phases with the macroscopic equivalent homogeneous material (EHM). Meanwhile, 3D Hashin-type damage initiation criteria were proposed to characterize the differences between the tensile and compressive strength of the EHM and fiber and their anisotropy feature. The cutting of the fiber and matrix phases under all cutting angles were divided into two simulation processes to improve the computational efficiency. With the help of this model, the thrust force was accurately predicted where the distribution of burrs was successfully simulated compared with the experimental measurements. In addition, the evolution process from the failure of the fiber and matrix phases towards formation of the burrs was clarified. It could be seen that in the drilling of the CFRPs at the hole exit, the matrix was removed while the fibers deformed out-of-plane under the push of the drill firstly rather than got removed and then bent with the rotation of the drill. Specifically, the fibers under acute cutting angles bent outward the hole radially, which made them more difficult to be removed and hence resulted in the burrs eventually. The revealed formation mechanisms would be the crucial contribution and guidance for helping to suppress the burrs.