Improving adhesion of hybrid Ti-CFRP joints obtained by direct co-bonding technique through laser surface treatments

• Two laser treatments (texturing and cleaning) were developed. • The process parameters affecting the texture geometry were studied. • Ti-CFRP Joints were produced by direct co-bonding after different laser treatments. • Laser treatments increase the strength and failure energy up to 6.5 and 65 times, respectively. • The maximum strength (18 MPa) is comparable to that obtained with structural adhesives. The paper focuses on the development of a laser-based surface treatment aimed at enhancing the adhesive strength of Ti6Al4V alloy-CFRP joints manufactured through direct co-bonding. To this end, the effect of process parameters on the groove geometry (depth, width, taper angle, and burr) that forms the texture was studied using ANalysis Of VAriance (ANOVA) and Response Surface Methodology (RSM). Two groove geometries were selected and adopted to produce two textures that differed in groove width and were similar in groove depth and filling factor. In addition to the two textures, a laser cleaning treatment was developed to treat the untextured area. Single lap joints were produced by adopting the two textures, both with and without laser cleaning treatment, and tested according to the ASTM Standards. The joints were obtained by direct co-bonding during the fabrication of CFRP through infusion techniques. Additionally, specimens subjected solely to laser cleaning and sandpaper abrasion were produced and designated as reference samples. Differences among the treatments with respect to strength and failure energy were evaluated using a one-way ANOVA and Tukey’s method for multiple comparisons. Results show that, compared to the sandpaper treatment, the laser cleaning treatment increases joint strength and failure energy by approximately 3 and 20 times, respectively. By adopting laser texturing, strength and failure energy increased by up to 6.5-fold and 75-fold, reaching approximately 18 MPa and 23.17 J, respectively. These values are comparable to those observed for similar joints in the main bibliography.