Laser-induced paint removal of CFRP composite skin without damage of interface aluminum layer

Avoiding substrate damage is of the utmost importance throughout the paint removal process. Laser technology enables accurate and effective paint removal. In this study, a two-step laser process was employed to remove the thick paint from the sprayed aluminum surface with a rough structure. As a result of high energy density laser induced, three uneven layers of paint were cleaned swiftly. The paint temperature quickly exceeded 450 K, and evaporation occurred. However, ablation removal took the lead in the experiments. Following the first removal, the surface treatment agent covered the ablation surface. Meanwhile, thermal accumulation caused formation and spreading of both poriferous and dense char-slag types over the aluminum surface. The surface treatment agent prevented direct interaction between laser and aluminum. The low energy density laser was then used to remove the remains. Except for the treatment agent hidden in recessed structures, the majority of residue was successfully removed at a laser energy density of 6.8 J/cm2. However, two types of damage manifest on the aluminum surface. Once the laser energy density reached 10.2 J/cm2, residual paint and remelting metal existed on the surface simultaneously. As the heat input was increased, the aluminum remelted and mixed with the residue, and a smoother aluminum surface was obtained. This two-step laser paint removal approach provides guidelines for using laser technology in aircraft restoration.