Effects of CFRP chip particle size on surface chemical activity during high-speed cutting: underlying mechanisms

During high-speed cutting of carbon-fiber-reinforced polymer (CFRP), intensive thermomechanical coupling generates chips with markedly different particle sizes and surface activities. Here, the relationship between chip particle size and surface chemical evolution was investigated by combining particle-size analysis, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, cutting-force measurement and infrared thermography. The chips showed a broad size distribution, with D10, D50 and D90 values of 14.88, 110.8 and 325.4 µm, respectively. Decreasing particle size led to progressive depletion of nonpolar C-C species and enrichment of oxygen-containing surface functionalities. FTIR further revealed cleavage of C-O-C linkages accompanied by enhanced carbonyl absorption, indicating simultaneous molecular-chain scission and surface oxidation. Mechanistic analysis showed that high-strain-rate shearing, localized thermal softening and fiber/matrix interfacial debonding jointly controlled particle refinement, whereas increased specific surface area, mechanochemical activation and localized oxidation promoted the formation of chemically active surfaces. These findings establish a mechanistic relationship between chip fragmentation and surface activation during high-speed CFRP cutting and provide guidance for the graded recycling and value-added utilization of CFRP machining waste.