Experimental and Theoretical Investigation of Laser Pretreatment on Strengthening the Heterojunction between Carbon Fiber-Reinforced Plastic and Aluminum Alloy

Besides aluminum alloys, lightweight carbon fiber-reinforced plastics (CFRPs) have been adopted progressively in automobiles to save energy and reduce emission, so constructing a reliable heterojunction between aluminum alloys and CFRPs has come to be the key issue. In this study, ultrafast picosecond infrared (IR) and excimer ultraviolet (UV) lasers were introduced to pretreat the joint surface to enhance the adhesive strength. Scanning electron microscopy, white light interferometry, and X-ray photoelectron spectroscopy examinations indicated that because the energy absorptivities for the two lasers were different, the variation of the roughness, wettability, and chemical composition were a little different for the patterned surface. Correspondingly, the shear strengths of the adhesive joints were increased from 5.6 to 24.8 and 21.9 MPa for IR and UV laser-pretreated samples, respectively. Furthermore, finite element analysis was adopted to evaluate the effects of strengthened mechanical interlocking and fortified chemical bonding force on the enhancement of joint strength. It was shown that chemical bonding, instead of mechanical interlocking, played the dominant role in reinforcing the heterogeneous joints. As a whole, the picosecond IR laser was more preferable for surface pretreatment in adhesive heterojunctions due to its higher processing and enhancing efficiency.