Experimental Study of Micro-Milling Carbon Fibre Reinforced Composites Under Variable Cooling And Lubrication Strategies

Carbon Fibre Reinforced Polymer (CFRP) is susceptible to localised damage from the cutting forces and heat generated during machining. Due to the hygroscopic nature of CFRP, conventional cutting fluids are not suitable for machining CFRP. Cryogenic cooling machining can minimise thermal damage to carbon fibre-reinforced plastics using cryogenic media instead of traditional cutting fluids. This study examines the milling performance of carbon fibre-reinforced plastics under various cooling and lubrication strategies. For this, four different cooling and lubrication strategies were set up and tested for micro-milling: dry normal temperature (Dry), cryogenic air (CA), minimal quantity lubrication (MQL), and cryogenic air minimal quantity lubrication (CA-MQL) to achieve high-quality and low-damage machining of CFRP. The study shows that the anisotropic cutting forces under MQL strategy are significantly reduced, F_x, F_y and F_z are reduced by about 36.12%, 32.64% and 36.36% respectively compared with dry micro-milling; the size of the delamination factor is MQL < CA-MQL < Dry < CA and the different cooling and lubrication strategies have a more significant influence on the surface quality of micro-milled grooves, among which, the Ra is relatively the lowest in the CA-MQL strategy, which is reduced by about 36.1% compared with dry micro-milling, can be reduced by about 18.4% compared with CA-assisted micro-milling, and can be reduced by about 27.9% compared with MQL-assisted micro-milling; the tool wear was different, but the general trend was similar. The results suggest that CA-MQL has a broad potential for application in the auxiliary machining of CFRP and other composite materials.