Aiming at the problems of low efficiency and serious tool wear in the drilling large hole for aviation large and complex carbon fiber reinforced polymer (CFRP)/titanium alloy (TC4) laminated stacks, a new process of robot laser and side-milling compound drilling is proposed, which has the advantages of high surface quality, high precision of geometry and high efficiency. laser and side-milling compound drilling experiment of CFRP/TC4 laminated stacks was carried out, and the effect of process parameters on the processing quality was explored. A Ø15 mm high precision hole was drilled on an 8mm CFRP/TC4 laminated stacks. Experimental results show that laser-induced heat affected zone (HAZ) can greatly reduce the cutting force during the milling process, the average cutting force of CFRP is reduced by 60.8%, and the average cutting force of TC4 is reduced by 66.2%. The introduction of minimal quantity lubrication (MQL) can greatly improve the surface quality. The surface roughness (Sa) of CFRP and TC4 decreasing by 36.1% and 36.8%, respectively, compared with dry cutting, and both remaining below 3.2 μm. The minimum interlayer burrs of CFRP and TC4 are 26.734 μm and 60.802 μm respectively.

To mitigate the high drilling temperatures and extensive machining damage associated with CFRP/titanium alloy laminated materials, a new robotic high and low frequency compound vibration-assisted drilling method has been developed. To assess the effectiveness of this process, a comparative experimental study was performed, comparing four machining techniques: conventional robot drilling, robotic high-frequency vibration drilling, robotic low-frequency vibration drilling, and robotic high and low frequency compound vibration-assisted drilling. The study evaluated drilling force, titanium alloy cutting temperature, titanium alloy chip morphology, the quality of CFRP holes, and the quality of Ti holes walls. The experimental results show that among the four processing methods, the high and low frequency compound vibration-assisted drilling by the robot can effectively reduce the axial force during drilling; the high and low frequency compound vibration-assisted drilling by the robot significantly reduces the cutting temperature of titanium alloy, with a maximum reduction of 31.25% compared to conventional robot drilling; the titanium alloy chips produced by the robot's high and low frequency compound vibrationassisted drilling are fan-shaped and the smallest in size; the high and low frequency compound vibration-assisted drilling by the robot significantly improves the CFRP hole edge damage and hole wall quality at low feed rates; the high and low frequency compound vibrationassisted drilling by the robot can significantly improves the quality of titanium alloy hole walls at low feed rates. Moreover, this improvement remains evident as the feed rate increases.

Carbon fiber reinforced polymer (CFRP) is widely used in aircraft manufacturing field because of superior physical and mechanical properties. Millions of connection holes require to be drilled on CFRP material, the cutting damage of holes has crucial effect on the aircraft performance. Robotic rotary ultrasonic drilling (RRUD) as a potential method is proposed to improve the drilling quality. Nevertheless, it is difficult to control the drilling temperature to avoid exceeding the glass transition temperature of the resin matrix in a dry cutting environment during RRUD. The minimum quantity lubrication (MQL) technology can improve cooling conditions and achieve temperature reduction effectively. In this paper, an investigation on cutting temperature during the processing method combining RRUD and MQL (RRUD&MQL) is carried out and a theoretical prediction model is established. Firstly, analysis on RRUD&MQL coupling friction reduction mechanism is conducted with consideration of periodic kinematics characteristic in RRUD and lubrication property of MQL droplets. After that, based on this friction reduction mechanism, thrust force is calculated and cutting temperature model is established. Finally, validation experiments results indicate that analytical cutting temperatures agree well with the experimental value, and the average of relative prediction error is 9.12%.

Carbon fiber-reinforcement plastics (CFRP) have been widely applied in modern aerospace industry with aluminum alloy in the form of thin-walled stacks due to their superior mechanical and physical properties. However, for CFRP, the heat accumulation occurs easily during countersinking process in consequence of low thermal conductivity. The surface thermal damage of CFRP caused by excessive heat would affect the fatigue and stealth performance of aircraft. Consequently, the countersinking temperature is an important indicator to judge the feasibility of CFRP countersinking process. In this paper, to investigate temperature of countersinking process, the application of rotary ultrasonic machining technology to CFRP/Al thin-walled stacks countersinking process under different stiffness conditions with drilling-countersinking integrated tool is carried out by FEA (Finite element analysis) and experiments. And the influences of cutting temperature on countersunk wall quality are discussed. The results demonstrate that the maximum countersinking temperature increases with the decrease of axial stiffness, and the ultrasonic vibration can effectively reduce maximum countersinking temperature by 22.9%-26.2%. Furthermore, analysis of the surface quality of countersunk wall shows that the countersunk wall roughness and defects gradually deteriorate with the increase of the maximum countersinking temperature. Meanwhile, the ultrasonic vibration can improve countersunk surface quality by reducing maximum countersinking temperature effectively.