Circular cutting strategy for drilling of carbon fiber-reinforced plastics (CFRPs)

The drilling process of carbon fiber-reinforced plastics (CFRPs) is the most commonly employed machining operation due to the necessity of joining these materials. However, these materials are prone to delaminate during the process, and the presence of this defect is the most cause of rejection for CFRP products, especially those produced for the aeronautic industry. Therefore, this article aims to study a drilling strategy (named circular drilling strategy) by using dedicated tools with different diameters, in order to reduce the extension of delaminations. Holes with different diameters (6, 8, and 10 mm) were obtained both with the conventional and with the proposed drilling strategy under distinct cutting conditions that mainly differ in the feed rates (62, 125, and 250 mm/min) and cutting velocities (50, 75, and 100 m/min). The effect of the cutting parameters and tool diameter on the cutting forces and delamination factor was studied for both the conventional and circular drilling process. The results proved that the proposed technique produces better hole quality and lower thrust forces than the conventional one under the same cutting conditions.