Gecko-inspired laser-textured titanium surface boosts composite laminate bonding by 202%

The research team, led by Fangting Qu and Chunming Ji with colleagues including Hongbo Huang, Yingze Li, Xiaodong He and Bing Wang, reports that a carefully engineered hierarchical surface on titanium raised the apparent interlaminar shear strength of the laminate from 29.27 MPa to 88.39 MPa, an increase of 201.98%. Failures in these laminates tend to occur as delamination at the metal-composite interface, which undermines the very reason for combining the two materials. The first scale is microscale.

Using laser-induced micro-texturing, the researchers engraved ordered grooves into the titanium plate, systematically varying groove depth and spacing to map how geometry affects bonding. The second scale is nanoscale. Onto the laser-textured surface they grew highly ordered arrays of titanium dioxide nanotubes using a two-step anodic oxidation process, so that the nanotubes formed both on the flat surface and inside the microgrooves.

Characterization of the treated surfaces showed that the uniform, ordered TiO2 nanotube arrays formed successfully within the grooves and across the plate. The team then measured how the surface interacted with liquids, a key indicator of how well molten PEEK would wet and infiltrate the texture during bonding. Within the investigated parameter range, the best performance emerged at a groove depth of 15 micrometers and a groove spacing of 1.0 millimeter.

Under that condition, the water contact angle dropped to 14.59 degrees, indicating a strongly hydrophilic surface, and the surface free energy reached 83.25 mJ/m2. Those surface changes translated directly into mechanical performance. The apparent interlaminar shear strength of laminates built on the optimally textured titanium reached 88.39 MPa, the 201.98% increase over the untreated baseline of 29.27 MPa.

The authors attribute the gain to a combination of effects working in concert: microscale mechanical interlocking as PEEK flows into the laser-cut grooves, nanoscale anchoring as the polymer penetrates the TiO2 nanotube pores, improved wettability, and a larger effective bonding area created by the texture. Fracture surface analysis provided visual support for that mechanism. Microscopy revealed PEEK retained inside the laser-induced micro-textures after failure, and the authors report morphological evidence suggesting possible PEEK penetration into the nanotube nanopores, forming what they describe as a multiscale mechanical interlocking effect.

Importantly, the treatment changed not just how strong the interface was but how it failed: the dominant failure mode shifted from interfacial delamination to cohesive and mixed failure modes, meaning the bond line itself became stronger relative to the materials it joins. The study is a laboratory-scale materials engineering investigation, and its conclusions are bounded by the parameter ranges the team tested; the reported optimum of 15 micrometer depth and 1.0 millimeter spacing applies within that window rather than as a universal rule. The article was published open access on 27 October 2026 as a peer-reviewed accepted manuscript shared ahead of final version-of-record edits, so some details may be refined in the final version.

The fracture-surface evidence for nanotube infiltration is described as suggestive rather than definitive, and the authors frame it as morphological support for the interlocking hypothesis. Even with those caveats, the approach stands out for its controllability. The authors position the work as an integrated and controllable micro-nano interface engineering approach for manufacturing CF/PEEK-titanium hybrid laminates with excellent interlaminar behavior.

Subject of Research: Gecko-inspired hierarchical surface engineering of titanium for CF/PEEK hybrid laminate interfaces

Article Title: 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

Article References: Qu, F., Ji, C., Huang, H., Li, Y., He, X., & Wang, B. (2026). 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. Advanced Composites and Hybrid Materials. https://doi.org/10.1007/s42114-026-02150-6

Image Credits: AI Generated

DOI: 10.1007/s42114-026-02150-6

Keywords: gecko-inspired materials, CF/PEEK, titanium, hybrid laminates, TiO2 nanotubes, laser texturing, interlaminar shear strength, surface wettability, mechanical interlocking, anodic oxidation, composites, interface engineering