Study on drilling force and export defects of CFRP composites in RULTVD

Carbon fiber reinforced polymer (CFRP) composites have been extensively utilized in the aerospace industry due to their exceptional mechanical and physical properties. However, the drilling process of carbon fiber composites is challenging due to their structural anisotropy, abrasiveness, and low thermal conductivity. To enhance processing quality, rotary ultrasonic longitudinal torsional vibration drilling (RULTVD) technology is employed for CFRP composite processing. Based on kinematics principles, a kinematics model of a single cutting edge is established, and the influence of separation characteristics on RULTVD machining is discussed. The effects of spindle speed, feed rate, and longitudinal-torsional amplitude on cutting force and hole export defects are investigated through experimental methods. The experimental results demonstrate that ultrasonic longitudinal-torsional drilling reduces the cutting force by 17.8 % compared to conventional drilling while decreasing the maximum delamination factor by 8.6 %. These findings validate that rotary ultrasonic longitudinal-torsional drilling significantly alleviates the processing challenges associated with carbon fiber reinforced composites while improving processing quality.