Study on ultrasonic vibration-assisted drilling process and surface quality of KFRP

Kevlar fiber reinforced polymer (KFRP) is widely used in aerospace and defense industries due to its excellent properties such as low density, high specific strength, and high stiffness. However, it is prone to produce delamination, burrs and other processing defects during drilling, seriously affecting the service performance of the workpiece. The ultrasonic vibration-assisted drilling (UVAD) technique was used to study the drilling process and surface quality. A kinematic model of UVAD was established and used to analyze the machining characteristics of pulse cutting. To reveal the drilling effects of KFRP under CD and UVAD, the comparison experiments have been conducted, and the axial force, drilling temperature, exit delamination ratio, and surface morphology of the hole wall in the drilling process of KFRP have been deeply studied. The results show that compared to CD, UVAD can decrease the drilling force and exit delamination ratio by 4.8% and 17%, respectively, and can increase the drilling temperature by 11.8%, but the exit burr is significantly reduced and the drilling quality is significantly improved. In addition, the drilling axial force and the exit delamination ratio decrease with the increase of the spindle speed and increase with the increase of the feed rate. The results of the study can provide a useful reference for high-quality hole processing of KFRP.