Process optimization and performance verification of CFRP laser surface modification

Abstract

Adhesive bonding has gradually replaced mechanical connections as the primary method for composite material bonding, with surface quality being the key factor determining the effectiveness of composite material adhesion. Laser surface treatment, known for its green and precise characteristics, has garnered widespread attention from both academia and industry. However, the process parameters of laser surface treatment are complex, efficiency is low, and the mechanism remains unclear. This paper, based on the response surface methodology (RSM), investigates the influence of laser secondary parameters on the resin removal rate of carbon fiber reinforced polymer/plastic (CFRP) surfaces and the impact of defocusing on surface treatment efficiency. The results indicate that when the total laser energy density (Et) is 69 J/cm2, the overlap ratio in the warp direction (OLs) is 76%, and the overlap ratio in the weft direction (OLh) is 85%, the surface tensile shear strength increases by 90.59% and 27.77% compared to the original surface and polished surface, respectively. When the defocus distance is +8 mm, the efficiency of laser surface treatment is 2.25 times that of non‐defocus, with minimal impact on mechanical performance. The surface treatment mechanism, with changes in Et, primarily involves the pure thermal decomposition of the resin matrix in an oxygen‐free environment, oxidative decomposition, and the synergistic action of the decomposition products' oxidation. Through the coupled optimization of laser process parameters, this work enhances the efficiency and effectiveness of composite material adhesive surface treatment, promoting the engineering application of laser technology.Highlights By establishing a response surface model, the study elucidated the impact patterns of laser secondary parameters (overlap rates in the warp and weft directions, total energy density) on the resin removal rate of CFRP surfaces. Based on the laser surface treatment phenomena at different total energy densities, the study analyzed and revealed the mechanism of near‐infrared (1064 nm) laser resin removal from CFRP surfaces. By increasing the spot size through defocusing, the efficiency of laser surface treatment was enhanced, and the impact on the interfacial properties of CFRP after defocused treatment was validated.