Experimental study on rotary longitudinal-torsional ultrasonic machining of unidirectional CFRP

Addressing the challenges of high grinding temperature, poor hole quality, and tool rod blocking in core drilling of carbon fiber reinforced plastics (CFRP), this study investigates the material removal characteristic of rotary longitudinal-torsional ultrasonic machining (RLTUM) of CFRP based on the Hertz contact theory. The study also conducts relevant experiments to compare and analyze the grinding force, grinding temperature, hole wall quality, exit quality, and tool wear in ordinary core drilling (OCD), rotary ultrasonic machining (RUM), and RLTUM of CFRP. The results demonstrate that RLTUM significantly reduces the grinding force, grinding temperature, hole exit damage and improves the surface smoothness of the CFRP hole walls. By utilizing intermittent cutting in circumferential direction for torsional vibration, RLTUM enables automatic removal of rod chips while restraining tool chip adhesion and reducing heat generation as well as tool wear. Therefore, RLTUM shows great potential for enhancing the quality of hole-making in CFRP.