The cutting force and defect analysis in milling of carbon fiber-reinforced polymer (CFRP) composite

Carbon fiber-reinforced polymer (CFRP) composite parts are usually made as near-net shape in aerospace and astronautic industry. However, mechanical machining such as milling is often required for part finishing in order to meet the dimensional accuracy before assembly. The milling process is vulnerable to damage like fiber breakage and pullout, and delamination. The cutting force is generally recognized as an indicator of machinability for milling of CFRP. In this study, slot milling of unidirectional CFRP was conducted with different cutting orientations and conditions. The patterns of cutting force and resulting defects along with the inherent mechanism are investigated. A mechanistic milling force model is proposed in which the specific cutting energies are modeled and calibrated considering the instantaneous chip thickness, fiber cutting angle, and cutting speed. The model is applicable to force prediction in milling both unidirectional CFRP and multi-directional CFRP.