Drilling Performance Evaluation and Mechanism Analysis of Diamond-Coated Drills in Ice-Supported CFRP Machining

Diamond-coated tools are suitable for CFRP machining because of their high hardness, sharp cutting edge, and good wear resistance. However, the anisotropic and heterogeneous nature of CFRP makes drilling-induced defects, such as burrs, tearing, fiber pull-out, and delamination, difficult to avoid, especially at the hole exit. In this study, an ice-supported drilling method was proposed for CFRP hole machining using diamond-coated drills. An ice layer was formed beneath the CFRP laminate to provide simultaneous low-temperature cooling and mechanical support during drilling. Comparative drilling experiments were conducted at spindle speeds of 400, 1200, and 2000 r/min. The results showed that the ice-supported drilling method markedly improved the hole surface quality and inner-wall integrity of CFRP laminates. Compared with conventional dry drilling, the drilling temperature was reduced by 22.03%, 10.70%, and 11.45% at 400, 1200, and 2000 r/min, respectively, while the hole-exit delamination factor decreased by 41.68%, 27.45%, and 57.04%, respectively. Moreover, after the same number of drilled holes, the diamond-coated drill used under ice-supported conditions exhibited less severe surface wear and cutting-edge blunting than that used under conventional dry conditions. The observed improvements were interpreted as being associated with the combined thermal-regulation and temporary mechanical-backing effects of the ice-supported condition.