Investigation of ultrasonic vibration-assisted laser texturing and adhesion of TC4/CFRP substrates for their bonding strength

This research presented ultrasonic vibration-assisted laser texturing (ULT) and adhesion (ULTA) of Ti-6Al-4 V (TC4) and CFRP substrates for the enhancement of single-lap bonding strength. As the ULT parameters were set to laser power of 27.2 W, scan speed of 100 mm/s, and ultrasonic power of 100 W, the maximum surface roughness and minimum water contact angle of TC4 and CFRP were 14.2 ± 1 μm and 31.4 ± 1.5 μm and 33.1 ± 1.7° and 10.1 ± 1.5°, respectively. Before and after the aging test, the maximum shear strength (Sm) of the ULTA single-lap TC4/CFRP joints was 9.81 ± 0.225 MPa and 7.47 ± 0.094 MPa, respectively, which demonstrated excellent shear strength and durability compared with the untextured and ULT joints. This was due to the increase in mechanical interlocking strength at the interface of the adhesive zone. Furthermore, the FTIR-analyzed results revealed that the epoxy resin adhesive underwent a hydrolysis reaction under high-temperature and high-humidity conditions, resulting in the breakage of chemical bonds in the molecules and affected its structure and composition. The Sm error of the untextured, ULT, and ULTA joints between the tensile test and the finite element analysis was less than 7%, which demonstrated a high prediction precision.