Abstract: The adhesive bonding pretreatment is an important process in the aerospace composites bonding. The bonding strength of the material is affected by surface morphology of the pretreated composite material directly. Based on ultraviolet (UV) pulsed laser cleaning technique of composite material, the effects of UV laser power and scanning speed on carbon fiber reinforced polymer (CFRP) surface morphology were studied by analyzing the laser cleaning microstructure of material surface under different process parameters, and also, comparison were made between single lap shear strength of bonded coupons pretreated by laser with those by other methods. The results show that when the laser frequency is 60 kHz and the scanning speed is 300 mm/s, the CFRP surface resin and interstitial resin are removed with the increase of laser power. The resin in the interstices of fibers is cleaned completely by the UV laser with the power of 8.5 W. The resins on the surface and in the interstices of fibers are cleaned completely by the UV laser with the power of 13.6 W. When the laser frequency is 30 kHz and the laser power is 13.6 W, the surface residual resin increases with the rise of the laser scanning speed. When the laser scanning speed is 500 mm/s, the carbon fibers have good integrity, the surface resin distributes uniformly and the resin in the interstices of fibers is completely removed. Mechanical test results show that when the laser frequency is 30 kHz, the laser power is 13.6 W, and the scanning speed is 500 mm/s, single shear strength of bonded coupons treated by laser could reach a equal level of that treated by peel ply, with significantly optimized discrete values (CV values).

Key words: composite material, ultraviolet pulsed laser, laser cleaning, laser power, laser scanning speed, surface morphology