Evaluation of Diamond-Coated Tools in Drilling High-Strength CFRP Composites

High-strength carbon fiber reinforced polymers (CFRPs) are advanced superhard engineering materials being extensively utilized in modern aerospace industries but show poor machinability. The present paper aims to address the performance of the diamond-coated special tools on the machining properties of high-strength CFRP composites. The studied CFRP specimen was a multidirectional composite laminate fabricated by high-strength T700 carbon fibers and epoxy resin. The tool performance on the cutting of high-strength CFRPs was studied in terms of thrust force, specific drilling energy, surface defects status, and cut product quality. The results indicate that tool geometries significantly affect the composite cutting responses, and the step drill outperforms the candlestick tool due to the step-shaped structure that alleviates the severe interaction with the hard CFRP composite workpiece during the chip separation process. The CFRP composite is prone to serious surface flaws because of its inherent anisotropy and heterogeneity despite the use of diamond-coated tools. Moreover, well-designed geometrical modification of diamond tools can greatly improve the composite surface quality.