Performance and mechanism evaluation during milling of CFRP laminates under cryogenic-based conditions

Due to the hygroscopicity of CFRP, dry and/or near-dry cutting conditions instead of conventional flood lubrication is recommended for CFRP machining. However, thermal damage, poor surface integrity, and harmful dust occur when machining CFRP under dry conditions. To address the above problems, this paper aims to investigate the machining performance of CFRP laminates under cryogenic-based conditions, which are characterized as cryogenic supercritical carbon dioxide (scCO2) and vegetable oil-based cryogenic minimum quantity lubrication (CMQL). The milling temperatures, milling forces, surface quality and surface generation mechanism were particularly studied to analyze the effect of cooling category on the milling performance of CFRP under varying cutting parameters. To reveal the underlying mechanisms of performance evolution with different lubri-cooling conditions, the basal tribology and wettability tests were innovatively carried out as a function of lubri-cooling environments. Results indicate that the minimum milling forces, milling temperatures and machined surface roughness were obtained under CMQL condition. Cryogenic cutting operation reduces the cutting temperature, increases the cutting force while improves the surface quality. The mechanism of material removal is significantly different under different tool-fiber angles. This study also demonstrated the feasibility of cryogenic cutting, especially CMQL condition to improve the surface quality during CFRP precision machining.