Study on picosecond laser processing of blind holes in carbon fiber-reinforced plastics

In view of the rough and sunken bottom of blind hole during the laser processing on carbon fiber-reinforced plastics (CFRP), a processing experiment with different hatch distance is conducted by picosecond laser, and the numerical simulation is carried out by COMSOL. The effects of scanning path distribution of hatch distance with equal and variable hatch distance in the processing depth, heat-affected zone and bottom micro-morphology of blind holes are studied. The results show that the variable hatch distance machining path can make heat more uniform on the material, so that the concave effect of the inner ring bottom is weakened. Moreover, the variable hatch distance path can reduce the fiber breakage and resin residue of blind holes, and enhance the physical performance of the structure. When the processing path is three sets of concentric circles with 70 µm innermost hatch distance and 100 µm outermost hatch distance, the machining depth can be achieved, and high-quality blind hole can be obtained under the premise of smaller heat-affected zone and borehole taper.