Study on chisel edge drilling behavior and step drill structure on delamination in drilling CFRP

Abstract In this paper, a twist drill was used to drill carbon fiber reinforced polymer composite (CFRP) materials to study the influence of the chisel edge drilling behavior on delamination at different parameters. The test results show that a high spindle speed is beneficial to the chisel edge to remove the material when the chisel edge is about to drill the bottom of the plate, and the chisel edge drilling behavior has important effect on delamination. In order to reduce the impact of chisel edge on delamination, three kinds of step drills (different ratio of primary drill bit diameter to secondary drill bit diameter ( k )) were designed to drill CFRP at different cutting parameters. The method of combining theory with practice is used to analyze delamination of step drill, and to optimize the step drill structure. Experimental results demonstrates that the hole entry quality of the step drills are better than that of the twist drill. k has great impacts on hole exit delamination. The step drill, k is about 0.5, can achieve the best hole exit quality under the large processing parameters, therefore it's suitable for drilling of CFRP.