An economical surface treatment for improving resistance welding strength of carbon fiber/epoxy composites

This study proposes an acid-etching surface treatment technology for treating the surface of carbon fiber/epoxy composites (CF/EP) to improve their physical and chemical properties, thereby achieving good adhesion with thermoplastic resins and high-quality resistance welding of CF/EP. The research shows that treating the CF/EP surface with concentrated sulfuric acid at 50°C for 45 minutes can significantly improve the single lap shear strength (LSS) of the CF/EP welding joint to 21.47 ± 1.2 MPa, which is 163.11% ± 14% higher than the LSS of the untreated sample. The acid etching surface treatment technology proposed in this paper is low-cost, simple to operate, and easy to replicate, combining innovation, feasibility, and economy. By analyzing the surface morphology, wettability, and chemical groups of the surface-treated samples, it can be seen that acid-etching treatment at an appropriate temperature and for a reasonable time can increase the surface roughness of CF/EP and introduce oxygen-containing chemical groups to the CF/EP surface, enhancing the wettability of the CF/EP surface and thereby improving the physical embedding and chemical bonding capabilities of the CF/EP surface.