An Economical Surface Treatment for Improving Resistance Welding Strength of Carbon Fiber/Epoxy Composites

In this study, an Acid-etching surface treatment technique is proposed for treating the surface of Carbon Fiber/Epoxy Composites(CF/EP) to optimize its surface energy and chemical bonding ability for good bonding with thermoplastic resins (PA6), and consequently for high-quality resistance welding of CF/EP. It was shown that treatment of CF/EP surfaces with concentrated sulfuric acid for 45 min at 50°C significantly increased the single lap shear strength (LSS) of CF/EP welded joints to 21.47 ± 1.2 MPa, which is 163.11% ± 14% higher than that of the welded joints of untreated samples. The Acid-etching surface treatment technique proposed in this study is low-cost, simple, easy to reproduce, and combines 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 at appropriate temperature and reasonable time can improve the surface energy of the laminate and introduce oxygen-containing chemical groups on the surface of the laminate to enhance the physical embedding and chemical bonding ability of the laminate surface.