Study of Cutting Speed Variation in the Ultrasonic Assisted Drilling of Carbon Fibre Composites

Ultrasonic assisted drilling (UAD) has been proven effective for the thrust force reduction as compared to conventional drilling (CD) for same machining parameters. The following research was focused on the examination of exit delamination, machined surface and cutting temperature measurement in UAD and a comparison to that in CD at the cutting speeds of 0.942 m/min, 9.42 m/min, 94.2 m/min and 282.6 m/min at a constant feed rate of 0.05 mm/rev in the through-hole drilling of CFRP material. X-Ray computed tomography (CT) was used to identify the exit delamination, internal damage, circularity and center deviation in CD and UAD. A maximum of 82.8% reduction in the center deviation and 33.2% reduction in circularity of the holes were found when drilled in UAD as compared to those in CD. Furthermore, the cutting temperature in the drilling of CFRP has been measured and compared for both the cases of CD and UAD. Ultrasonic assistance produced 10°C higher cutting temperature than that in CD at the cutting speed of 282.6 m/min while at lower cutting speeds (0.942 m/min and 9.42 m/min), the cutting temperatures with and without ultrasonic assistance did not have a significant difference (2°C and 4°C respectively).