Study On The Effect Of Infrared Pulse Laser Paint Removal On The Recoatability Of CFRP Skin Spray Paint

The advantages of environmental protection,controllability and high precision of laser paint removal technology make it expected to replace the traditional mechanical grinding and chemical paint removal processes and effectively remove the paint layer on the surface of aircraft skin.At present,laser paint removal mostly takes single-layer paint removal on the surface of metal(aluminum alloy)skin as the research object,and there is little research on laser paint removal for the multi-layer coating system of composite structure skin surface,which is difficult to reveal the process and process parameters of layered and controllable paint removal on the surface of composite structure skin.Secondly,laser ablation and impact effects can also affect the surface performance of the retained paint layer,thereby affecting the recoating ability of the retained paint layer surface after paint removal.Therefore,clarifying the influence of laser paint removal on the recoating of composite structure skin spraying has become an engineering application problem that needs to be solved urgently to verify the correctness and rationality of laser paint removal process and realize automatic paint removal and airworthiness verification of aircraft skin.The paper focuses on the multiple paint layers on the surface of Carbon Fiber Reinforced Epoxy Plastics(CFRP)composite materials.Orthogonal experiments and single variable experiments were conducted using an infrared pulse fiber laser to investigate the effects of laser process parameters on the physical and chemical properties of the retained paint layer surface after laser delamination and paint removal.Based on this,the retained paint layer was repainted,Verify the adhesion and environmental durability of the new paint layer interface after paint removal.First,the paper analyzes the influence of laser process parameters on the paint removal effect through orthogonal experiments and single variable paint removal experiments.The results indicate that the average laser power and scanning speed have a significant impact on the paint removal effect,with the remaining surface roughness of the paint layer after paint removal as the evaluation indicator,followed by pulse frequency.When the energy density is maintained at 47.54 J/cm~2 and the scanning speed is 2800 mm/s,the layered paint removal effect is the best,and the paint layer thickness is preserved intact.Secondly,the effects of energy density and scanning speed on the surface roughness,wettability,and free energy of the retained paint layer after paint removal were studied.The results show that adjusting laser process parameters can change the surface roughness and wettability of the paint layer.Comparing the surface free energy of the paint layer before and after laser paint removal,it was found that the surface free energy of the paint layer after laser paint removal was 45.93 m J/m~2,which is higher than the 42.67 m J/m~2 of the original paint layer.The surface adhesion ability of the paint layer after laser paint removal is stronger,which is more conducive to repainting.Finally,based on the research on surface physicochemistry of the retained paint layer,the interfacial adhesion and environmental resistance of the retained paint layer to the new paint layer were studied.The results show that the retained coat is tightly bonded with the new coat and has no defects.The adhesion test result of the new coat is the highest grade 0 with a good adhesion.After the high-temperature and low-temperature aging test,no cracks,bubbles,shedding and other phenomena occur on the new paint layer,and the adhesion of the new paint layer is good.After UV accelerated aging test,the new paint layer and the original paint layer lose light level slightly and the color difference changes slightly.It shows that laser paint removal will not affect the interfacial adhesion and environmental durability of the paint layer after repainting.