The Influence of Cutting Parameters on Chip Morphology and Chemical Activity in High-Speed Turning of CFRP

Large amounts of chips are inevitably produced during machining of carbon fiber-reinforced polymers (CFRP), which urgently requires further investigation on recycling and high-value utilization. This study focuses on the effects of cutting parameters on chip morphology and chemical reactivity during high-speed turning of CFRP composites. Experimental results show that uniformly fragmented CFRP chips can be obtained at cutting speeds of 404 – 674 m/min, feed rates of 0.1 – 0.25 mm/r, and cutting depths of 0.1 – 0.25 mm. These chips are mainly composed of transparent resin flakes embedded with short carbon fibers. XPS examinations demonstrate that increasing cutting speed, feed rate, and cutting depth significantly promote the mechanochemical degradation of the epoxy matrix. The relative content of C=O increases from 4.51±0.19% to 7.69±0.15%, C-C increases from 59.78±3.10% to 77.10±1.51%, and C-O decreases from 35.71±3.01% to 15.67±1.43%. Cutting speed presents the dominant influence, while the effects of feed rate and cutting depth gradually stabilize beyond a critical threshold. FTIR analysis indicates that the ester C=O content increases greatly with cutting speed, slightly with feed rate, and is barely affected by cutting depth. All three cutting parameters shift the C=O absorption peak toward higher wavenumbers, enhancing the double-bond characteristics and chemical reactivity. A mechanism for the generation of active functional groups in CFRP chips is proposed: mechanochemical reactions occur in the epoxy resin within the primary deformation zone, induced by the coupled effects of high strain rate, mechanical stress, and temperature rise, leading to the breakage of cross-linked molecular chains and the formation of abundant oxygen-containing active groups.