Effects of surface treatments and adhesives on composite/steel joint performance under extreme temperatures

Composite-metal bonded structures are widely used in extreme working conditions such as aerospace and cryogenic energy storage. Optimizing bonding processes is critical to improving their service performance under extreme temperatures. This study investigates the coupling effects of surface treatments and adhesive properties on the interfacial performance of composite/stainless steel joints under cryogenic and high-low temperature conditions. Mechanical grinding, acid pickling, and atmospheric plasma treatments were employed to tailor surface wettability and morphology, while adhesives with different viscosities were adopted to regulate interfacial infiltration behavior. Results showed that mechanical grinding significantly enhanced surface roughness and promotes mechanical interlocking. When combined with low-viscosity resin, it achieves the highest lap shear strength(LSS) and exhibits the most pronounced improvement under cryogenic conditions. In contrast, acid pickling and plasma treatments primarily improved surface activity and chemical bonding, but exhibited limited strengthening effects at low temperatures. Long-term cryogenic exposure caused interfacial degradation owing to thermomechanical mismatch and crack propagation, whereas subsequent thermal treatment partially restores bonding performance through post-curing and stress relaxation. The results reveal that bonding performance is governed by the synergistic interaction among surface roughness, wettability, adhesive viscosity, and thermomechanical effects.