Study on plasma behaviour, ablation mechanism, and surface morphology of CFRP by underwater laser-induced plasma micro-machining

Abstract

Carbon fibre-reinforced plastic (CFRP) is an excellent non-metallic composite material with advanced mechanical properties. Laser-induced plasma micro-machining (LIPMM) is a high-quality method of processing CFRP with less thermal damage. This study explored the interaction mechanism between plasma and CFRP material at different liquid depths and laser energies. A numerical model considering heterogeneity and anisotropy was proposed to study the anisotropic heat transfer of CFRP. The relationship between the plasma plume and material ablation was also investigated. The results revealed that a considerable ablation depth was obtained with a high aspect ratio of the plasma. In addition, the influence of surface tension on bubble attachment was studied, and it was found that decreasing the surface tension of a liquid could reduce bubble attachment. Machining CFRP by LIPMM in 40 % ethanol solution can effectively reduce the bubbles on the sample surface and improve the processing quality. As the thermal conductivity of the liquid medium is greater than that of the air, the thermal damage of epoxy resin was effectively reduced. The ablation depth with LIPMM increased by about 17.5 % compared to laser process in air.