Achieving High‐Strength Hybrid Titanium Alloy/ <scp>CFRP</scp> Structural Bonded Joints via Synergistic Mechanical Interlocking and Chemical Activation

ABSTRACT With carbon‐fiber‐reinforced polymer (CFRP) composites accounting for over 50% of next‐generation aircraft structures, adhesive bonding has become the optimal weight‐saving method for joining metallic components to CFRP in complex lightweight structures. Nevertheless, the lap shear strength (LSS) of conventional adhesive joints remains insufficient for high‐performance aerospace structural applications. To address this bottleneck, this study first explored the effects of bondline thickness and curing pressure on the joint LSS. On this basis, an interfacial synergistic reinforcement strategy integrating mechanical interlocking with chemical activation was proposed. A dual‐stage variable‐grit roughening process was employed to construct dual‐scale nested microstructures on the titanium alloy surface. Simultaneously, low‐pressure micro‐abrasive roughening created shallow microstructures on the CFRP, enabling efficient mechanical interlocking without damaging the load‐bearing fibers. Atmospheric‐pressure plasma treatment was then utilized to graft polar groups onto the surfaces, inducing a near‐superwetting state that significantly enhanced interfacial chemical bonding. This paper elucidates the underlying synergistic mechanisms through morphological, physicochemical, and fracture analyses. Consequently, the LSS of the reinforced joint reached an exceptionally high 48.5 MPa, representing a remarkable 117.5% improvement over untreated specimens. Ultimately, this methodology was successfully applied to the lightweight design of a representative complex dissimilar structure.