Comparative investigations on machinability and surface integrity of CFRP plate by picosecond laser vs laser induced plasma micro-drilling

Carbon fiber reinforced plastic (CFRP) is being widely used due to its excellent mechanical properties and corrosion resistance. However, CFRP with the characteristics of anisotropy and inhomogeneous result in difficulty to drill micro-holes. Traditional methods are used to drill micro-holes resulting in poor performance, such as fiber pull-out, tool wear, and bad processed surface quality. Laser machining has great potential on drilling CFRP micro-holes without tool wear and fiber pull-out, but leads to large taper and recast layer. In this study, laser induced plasma micro-drilling (LIPMD) was proposed to reduce the taper as well as improve the processed surface integrity. A comprehensive analysis processed sidewall surface quality, taper, roundness and surface integrity were conducted, and LIPMD process showed more advantages over laser in air (LIA). It is concluded that the processed sidewall machined by the LIPMD has less epoxy recast layer, and the surface of fiber is smoother than that of in the LIA process, diameter difference between the top and bottom of micro-holes is reduced by about 24.83%-32.02%, and the taper is reduced by 32.02%-47.44% compared with the LIA process. This investigation demonstrates the applicability of the LIPMD as a potential process for improved machinability and surface integrity of CFRP material.