This study investigates the impact of coupling agent-modified resistance welding heating elements on the welding strength of carbon fiber-reinforced polyamide 6 (PA6) thermoplastic composites. Silane coupling agent KH550 and titanate coupling agent UP-201 were used to modify heating elements made of 304 stainless steel mesh. Optimal modification parameters for KH550-modified stainless steel mesh (SSM) were determined using orthogonal experiments, resulting in maximum single lap shear strength (LSS) of 17.05 MPa under specific welding conditions. Comparative tests demonstrated the enhancement effect of UP-201-modified SSM on LSS. Additionally, two experimental schemes were used to study the synergistic enhancement effect of KH550 and UP-201 on the LSS of resistance welded joints. The findings indicate that both coupling agents improve the welding strength, with significant differences in their individual and combined effects. Highlights This study explores carbon fiber reinforced Nylon 6, an innovative thermoplastic. Analyzed effects of modified heating elements on joint shear strength. Examined silane and titanate coupling agents' effects on weld joint shear strength. Investigated synergistic effects of silane and titanate agents on weld joint strength. Investigated the synergistic enhancement mechanism of silane and titanate agents.
This study demonstrates effective resistance welding between 7075 aluminum (Al) alloy and carbon fiber/polyether ether ketone (CF/PEEK) composites by combining chemical etching and silanization surface treatments with a polyetherimide (PEI) thermoplastic layer. The effects of this hybrid treatment on the bonding at the 7075 Al alloy/PEI thermoplastic layer interface and the mechanical performance of the welded joints are systematically investigated. Chemical etching created a micro-nano rough surface that enhanced mechanical interlocking and increased hydroxyl group content from 12.7 mol% to 28.5 mol%. Subsequent silanization grafted amino ( NH 2 ) groups onto the 7075 Al alloy surface, enabling hydrogen bonding with the PEI thermoplastic layer. Under the synergistic effects of mechanical interlocking and hydrogen bonding, interfacial bonding is significantly enhanced, increasing the lap shear strength (LSS) of the joint from 0.2 to 24.6 MPa. The fracture failure mode of the welded joint changes from the interfacial failure of the 7075 Al alloy and PEI thermoplastic layer to the interlaminar failure of carbon fiber tearing in the heating element. Summary A new approach enables effective resistance welding of 7075 Al alloy and CF/PEEK composites. A hybrid surface treatment enhances 7075 Al alloy bonding with PEI thermoplastic layer. The hybrid surface treatment induces mechanical interlocking and hydrogen bonding effects. The synergistic effects can significantly enhance the performance of welded joints.
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.
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