Comparative study of drilling and plunge milling hole making in CFRP and AFRP

Carbon fiber reinforced polymer (CFRP) and aramid fiber reinforced polymer (AFRP) exhibit distinct material removal behaviors and damage characteristics during hole making because of the intrinsic differences in fiber properties; however, systematic comparative studies under unified machining conditions remain limited. In this work, at a constant spindle speed of 6000 r/min, a two-flute twist drill (AA-D) and two four-flute flat end mills (CFM-5 and CFM-4) were employed to comparatively investigate the drilling and plunge-milling hole-making behaviors of CFRP and AFRP over a feed range of 50–500 mm/min. Cutting force, machining temperature, entrance delamination factor, hole entrance and hole wall morphologies, and tool wear were systematically characterized. The results show that the axial force and peak temperature of AFRP are both significantly higher than those of CFRP. In particular, when CFM-5 was used, the peak Fz of AFRP was 66.7%–175.0% higher than that of CFRP, while its peak temperature was 116.7%–145.9% higher. The maximum entrance delamination factor of AFRP was 11.6% higher than that of CFRP. The hole-wall damage of CFRP was mainly characterized by delamination, peeling, and cracking, whereas that of AFRP was dominated by fiber pull-out, fuzzing, and tearing. The corresponding tool wear mechanisms were mainly abrasive wear and micro-chipping for CFRP, and material adhesion and edge blunting for AFRP. Overall, CFRP exhibited the most stable machining performance under CFM-5 at 50–90 mm/min, whereas AFRP achieved the best overall performance under CFM-5 at 300 mm/min. In general, CFM-5 provided superior hole-making performance for both materials, while AFRP showed markedly higher machining difficulty and process sensitivity than CFRP.