Grooving of CFRP with water mist jet–assisted nanosecond pulsed laser: effect of process parameters on removal mechanisms and HAZ formation

Carbon fiber–reinforced plastic (CFRP) processed by laser acquires a large heat-affected zone (HAZ) accompanied by mechanical corrosion due to overmelting and vaporization of the resin matrix. To reduce the thermal effect of laser processing CFRP, this paper investigates the use of siphoned water mist to cool the material. This involves directing a water mist jet at the CFRP, which forms a flowing water film on the surface. The droplets in the mist evaporate and convectively remove excess laser heat, reducing thermal accumulation damage. The effect of process parameters such as water mist jet angle, air pressure, offset distance, laser power, and frequency on the groove morphology and dimensional characteristics is experimentally investigated. The results show that the atomized droplet layer in the flow field of the water mist affects the laser energy transfer, while the velocity of the wall flow field helps to remove the ablated substrate. However, short pulse laser cycles can have a negative effect on controlling the HAZ of the groove. Herein, a finite element model of a siphon water mist jet is developed to simulate the distribution of water film and droplet atomization layer in the wall flow field. The experimental and simulation results demonstrate the potential of water mist jet-assisted laser ablation in enhancing the quality of CFRP cutting, but also highlight the negative effect of the droplet atomization layer in the wall flow field. Furthermore, an analysis has been conducted on the multi-stage, multi-factor coupled removal mechanism in water mist jet-assisted laser grooving of CFRP. This study emphasizes the potential benefits of water mist jet-assisted laser processing for CFRP and provides useful information for selecting process parameters.