Ultrasonic assisted pecking drilling process for CFRP/Ti laminated materials

Carbon fiber reinforced polymer (CFRP)/titanium alloy (Ti) laminated materials are widely used in aerospace and marine industries because of their excellent physical and electrochemical properties. The extensive demand requires a higher level of hole making technology to reduce the material damage caused by hole making. In this paper, we adopt a novel machining method, which combines Ultrasonic Assisted Drilling (UAD) and pecking drilling to generate a new machining method, Ultrasonic Pecking Drilling (UPD). Based on this, this study compares Conventional Drilling (CD), UAD and UPD in terms of thrust using orthogonal test method. In this paper, CFRP exiting delamination damage is investigated for three processing methods, and indirect measurement of interface temperature as well as detection of CFRP entrance delamination damage are carried out for UPD process. In addition, the tool wear and the exit burr of titanium alloy are analyzed for the three processes under different parameters. The test results show that UPD performed better in terms of thrust, the lowest thrust force is reduced by 35.1 % and 14.8 % at low feeds, respectively. CFRP exit delamination and tool wear are also good compared to both CD and UAD. Compared to CD, the maximum delamination damage decreased by 6.37 %. Besides, UPD results in better hole surface quality, where the roughness can be reduced by up to about 40 %. The obtained results show that UPD is a worthwhile option for drilling CFRP/Ti laminated materials.