The effect of laser ablation treatment on the chemistry, morphology and bonding strength of CFRP joints

The strength of carbon fiber reinforced polymer (CFRP) adhesive-bonded joints can be greatly improved by laser ablation treatment, which modifies the surface physicochemical properties. This study investigated the effect of laser ablation treatment on the chemistry, morphology and resultant bonding strength of CFRP joints. It was found that laser ablation treatment improved the lap-shear strength of adhesive-bonded CFRP joints from 8.5 to 30.4 MPa when a laser energy density of 35.4 mJ/mm2 was applied. X-ray photo electron spectroscopy (XPS) analyses and contact angle measurements revealed that the laser ablation treatment not only removed the release agent but also enhanced the wettability of CFRP surface. Scanning electron microscope (SEM) observation indicated that the optimal laser ablation treatment merely removed a layer of epoxy resin above the carbon fibers and exposed the undamaged carbon fibers. The exposure of carbon fibers greatly increased the bonded area between the adhesive and the CFRP substrate, which acts as an additional mechanism of improving the lap-shear strength of adhesive-bonded CFRP joints.