Tool wear in ultrasonic vibration-assisted drilling of CFRP: a comparison with conventional drilling

Carbon fiber reinforced polymers (CFRPs) are becoming increasingly prevalent in the industries including automobile, aerospace, and military due to their light quality, high specific strength, high corrosion resistance, excellent thermodynamics performance, etc. However, these excellent properties easily result in intensive tool wear, short tool life, and reduced machining accuracy. Although ultrasonic vibration-assisted drilling (UVAD) was considered an effective drilling method to reduce tool wear, most reported studies focused on machining kinematics or mechanics, and very few studies systematically explored the tool wear behaviors in UVAD of CFRP. To fill this gap, this paper aims to investigate tool wear of high-speed steel (HSS) twist drill in UVAD of CFRP and compares these wear behaviors with those in conventional drilling based on the experimental observation of the worn drill morphologies. The effects of cutting parameters on tool wear were discussed with the special focus on the differences in tool wear between conventional drilling (CD) and UVAD. The observed wear behaviors can include abrasion, adhesion, oxidization, or the combination of them. The introduction of UVAD can effectively reduce the average width of tool flank wear with a maximum reduction of 13.0% when compared with CD. Both increased feed rate and decreased spindle speed can lead to decreased tool wear. The findings in this paper might offer guidance on the selection of cutting parameters for extending tool life in UVAD of CFRP.