Effect of HF treatment on the bonding strength of laser-bonded Mg alloy/carbon fiber-reinforced plastic joint: XPS and NEXAFS study

This study investigated the effect of hydrofluoric acid treatment on the bonding strength of AZ31 carbon-fiber-reinforced plastic (CFRP) joints produced by thermal laser joining. Surface modification was performed to generate reactive sites for the promotion of chemical interaction with the CFRP, resulting in an enhanced interfacial adhesion. The improved interfacial adhesion and joint strength were determined by contact angle and tensile shear strength tests, respectively. Scanning electron microscopy (SEM) was used to investigate the joint interface and the fracture surfaces. The fracture surfaces were further analyzed using X-ray photoelectron spectroscopy (XPS) and near edge X-ray absorption fine structure spectroscopy (NEXAFS). The formation of C-F and MgO chemical bonds at the HF-treated AZ31/CFRP joint interface were found to be key factors influencing joint strength.