Experimental investigation and optimization in rotary ultrasonic drilling of C/C composites

C/C composites are widely used in aviation and aerospace due to their low density, superior specific strength, special elastic modulus at elevated temperatures, small thermal expansion coefficient and high fracture toughness. However, there are numerous problems such as delamination, chipping, poor machining quality and tool wear in drilling of C/C composites due to inhomogeneous, anisotropic, wear resistance and varying thermal properties of the composites. In this paper, related experiments on rotary ultrasonic drilling of C/C composites using diamond core drill were conducted to compare the drilling force and machining quality of ultrasonic drilling with conventional drilling, analyze the rotary ultrasonic drilling mechanism and research the influence of spindle speed, feed rate and ultrasonic amplitude on the drilling force. Experimental results showed that rotary ultrasonic drilling can significantly improve the removal of the chips thus preventing the core drill blockage, effectively reduce the drilling force and improve processing quality. In addition, the drilling force decreased with increasing of spindle speed and ultrasonic amplitude, while it increased with increasing of feed rate. Finally, the cutting parameters were optimized by consideration of the drilling force and efficiency.