Gecko-inspired tunable hierarchical interface for CF/PEEK-titanium hybrid laminates: synergistic enhancement via laser-induced micro-texturing and in-situ grown TiO2 nanotube arrays

A hierarchical micro-nano structure inspired by geckos was constructed on the titanium surface via laser-induced micro-texturing and in-situ growth of TiO2 nanotube arrays (TNTs). An effective strategy was proposed to enhance the interfacial bonding performance of carbon fiber reinforced polyetheretherketone-titanium (CF/PEEK-titanium) hybrid laminates. The influence of microgroove depth and spacing on the interfacial performance was studied, and highly ordered TNTs were fabricated using a two-step anodic oxidation process. The surface morphology, physical and chemical properties, surface wettability and interlayer bonding performance of the treated titanium plate were investigated. The results showed that highly uniform and ordered TNTs successfully formed in the microgrooves and on the surface. Within the investigated parameter range, the optimal performance is achieved at a groove depth of 15 μm and a groove spacing of 1.0 mm. Under this condition, the water contact angle decreased to 14.59°, the surface free energy reached 83.25 mJ/m2, and the apparent interlaminar shear strength (ILSS) attains 88.39 MPa, corresponding to a 201.98% increase relative to the untreated laminate. The fracture surface observation revealed PEEK retention within the laser-induced micro-texturing and provided morphological evidence suggesting possible PEEK penetration into the TNT nanopores, forming a multiscale mechanical interlocking effect, which transformed the dominant failure mode from interfacial delamination to cohesive and mixed failure modes. The synergistic effects of microscale interlocking, nanoscale anchoring, improved wettability and increased effective bonding area collectively contributed to the significant enhancement in interfacial strength. This study provides an integrated and controllable micro-nano interface engineering approach for manufacturing CF/PEEK-titanium hybrid laminates with excellent interlaminar behavior. A gecko-inspired hierarchical interface was constructed on titanium sheets. Laser-texturing and TiO2 nanotube arrays enable multiscale anchoring. The hierarchical interface improved ILSS by 201.98%, from 29.27 MPa to 88.39 MPa. Multiscale interlocking transformed failure from debonding to mixed failure.