Abstract: In the ultrasonic-assisted drilling of carbon fiber composite material (CFRP), the selection of the tool has a significant influence on the hole quality. To analyze the influence of different kinds of drills on ultrasonic-assisted drilling of CFRP, core drills, twist drills, improved twist drills, and dagger drills were selected to conduct comparison experiments under the conditions of different spindle speeds and feed rates. The results show that the thrust force and the exit delamination area during core drilling are significantly affected by the machining parameters. The high spindle speed and the low feed rate should be selected with the utilization of core drilling. There was no evident change in the delamination area caused by the other three tools with the increase of the spindle speed. According to the characteristics of the delamination morphology of hole entrances and exits, twist drills and improved twist drills are appropriate for the drilling process with low hole quality and moderate drilling efficiency. The dagger drill is suitable for drilling thin CFRP plates with the requirements of high hole quality and moderate drilling efficiency.

Key words: CFRP, ultrasonic-assisted drilling, delamination, tools