Variable amplitude drilling strategy for CFRP delamination suppression based on ultrasonic effects: Finite element simulation and experimental validation

Abstract

Carbon fiber-reinforced plastic (CFRP) composites are extensively applied in aerospace industry for their excellent mechanical properties such as high specific strength and high specific modulus. During the drilling of CFRP components, delamination is one of the most significant defects affecting their mechanical performance. Ultrasonic vibration-assisted drilling can effectively suppress delamination. However, there hasn't been sufficient exploration on how the ultrasonic vibration effect can improve the drilled hole quality considering the CFRP delamination mechanism. In this paper, a three-dimensional finite element model for CFRP laminates is established and validated. Subsequently, the delamination mechanisms at the entrance and exit of CFRP laminates are analyzed separately, and the influence of processing parameters on ultrasonic vibration effects are analyzed. In light of the mechanisms, a variable amplitude machining strategy for CFRP drilling delamination suppression is proposed based on ultrasonic vibration effects. Finally, experiments were conducted for conventional drilling (CD), ultrasonic vibration-assisted drilling (UAD), and varying amplitude ultrasonic vibration-assisted drilling (VAUAD). The VAUAD group exhibited a reduction of 63.8 % and 17.3 % in the mean square deviation of entrance delamination factors compared to the CD and UAD groups, and the mean square deviation of exit delamination factors decreased by 54.9 % and 23.9 % for the VAUAD group compared to the CD and UAD groups. These results validate the effectiveness of this strategy.