Surface microstructural design and hierarchical failure mechanisms of anodized CFRP/Al joints strengthened by growth of ZnO nanosheets and Resin-Pre-Coating with nano SiO2

To improve the bonding strength of CFRP/Al joints, a novel hierarchical interface through anodization, ZnO nanosheet growth and improved Resin Pre-Coating (RPC) with nano-SiO 2 is designed and its hierarchical failure mechanisms are studied. Porous Al substrates are prepared via anodization, followed by in-situ growth of ZnO nanosheets and infiltration of RPC solution containing nano-SiO 2 to enhance mechanical interlocking at nano-scale. Systematic characterizations including single-lap shear testing, SEM and XRD are conducted to evaluate interfacial morphology, wettability and mechanical properties. Results show that optimal porous surface microstructure and interfacial wettability are obtained by the effect analysis of anodizing time. In surprise, the combined treatment of ZnO nanosheets and improved RPC with nano-SiO 2 shows an increase in the shear strength over 400 % compared to untreated joints. Macro and micro failure modes reveal that the interfacial failure is transitioned to cohesive failure with fiber tearing and resin/SiO 2 interface debonding. The synergistic strategy effectively improves the hierarchical failure through enhanced nano-interlocking and adhesive reinforcement, offering a promising pathway for designing and manufacturing high-strength CFRP/Al joints.