Performance of high-frequency ultrasonic vibration-assisted drilling of ceramic matrix composites

Ceramic matrix composites (CMCs) are promising for manufacturing the high thrust-to-weight ratio aero engines. For the sake of assembly and cooling, it is necessary to drill holes in a CMC part. However, CMC is hard, brittle, and heterogeneous. The hole machining of CMCs is accompanied by low efficiency, uncontrolled drilling damage, and severe tool wear. Among the hole machining methods, ultrasonic vibration-assisted drilling (UAD) represents a huge potential for damage control and increased efficiency. However, most works on UAD use a fixed vibration frequency. This study tries to use high-frequency ultrasonic vibration-assisted drilling (HFUAD) to drill CMC holes. The drilling performance of HFUAD is compared with conventional machining (CD) and UAD by both experimental study and theoretical analysis. Results show that HFUAD reduces hole cylindricity errors by 65 % and 29 % compared with CD and UAD, respectively. By increasing ultrasonic vibration frequency, the highstress area during drilling is greatly reduced, leading to dramatic reductions in both drilling damage and drilling force. Moreover, HFUAD extends the drilling tool life more than 3.3 and 2.5 times compared with CD and UAD, respectively. HFUAD is demonstrated effectively in realizing high accuracy and low damage machining of CMC holes. Therefore, this study provides a new way to high-performance machining of CMCs.