Constructing spider-web-like PVDF fiber film via electrospinning and resin pre-coating for enhancing interfacial bonding between titanium alloy and CFRP

Reliable bonding between titanium alloy (Ti) and carbon fiber reinforced polymer (CFRP) is crucial in applications such as aero-engine blades. However, the smooth native oxide film on the Ti substrate surface and the inherent brittleness of the epoxy adhesive layer can readily lead to interfacial debonding failure. This study proposed an integrated surface treatment process combining laser engraving, electrospinning, and resin pre-coating (RPC). Laser engraving was employed to generate regular protrusions and micro-channels on Ti substrate surface, thereby providing mechanical anchoring sites and quasi-vertical infiltration spaces for epoxy resin. Electrospinning was then utilized to deposit a polyvinylidene fluoride (PVDF) fiber web with a controllable areal density (0.2–1.0 g/m 2 ) onto the engraved surface, forming a three-dimensional porous network. Subsequently, the RPC treatment reduced the micro-void defects caused by the intrinsic hydrophobicity of PVDF, ensuring improved resin infiltration and establishing quasi-Z-directional fiber bridging. This approach was designed to construct a spider-web-like PVDF fiber film reinforcement structure at the bonding interface. Surface analysis demonstrated that the combined treatment effectively modulated the surface morphology, roughness, and wettability. Single lap shear tests revealed that the PVDF 0.4 -Ti/CFRP composite (laser engraving + 0.4 g/m 2 PVDF fiber web + RPC) achieved a shear strength of 26.8 MPa, representing a 137.2% increase over the untreated control. Failure mode analysis further revealed that the failure mechanism transitioned from interfacial debonding to CFRP interlaminar tearing, confirming the effectiveness of the PVDF fiber web as an interfacial reinforcement and providing a new pathway for high-performance Ti/CFRP joining.