Metallization on CFRP: Effect of Interlayers and Deposition Methods for Aerospace Applications

Abstract Carbon fibre reinforced polymers (CFRPs) are increasingly used in aerospace structures owing to their high specific strength and low weight. However, their limited electrical conductivity and anisotropic current transport capability make them susceptible to lightning strike damage, creating a need for conductive and mechanically durable metallization strategies. Effective metallization of CFRP remains challenging due to low surface energy, anisotropy, and thermal sensitivity. This study investigates multilayer metallic coating architectures using Zn, Zn/Al, and Zn/Cu transition layers deposited by arc wire spraying (AWS), combined with Al or Cu topcoats applied via high-pressure cold spraying (HPCS), to improve adhesion and mechanical durability. Adhesion was evaluated through pull-off testing and microstructural analysis. Zn interlayers consistently outperformed Zn/Al (~7 compared with ~ 4-5 MPa). Al topcoats reached 8.4 MPa on four-layer Zn/Al interlayers, whereas Cu topcoats reached 12.1 MPa on four-layer Zn interlayers. Incorporating a Zn/Cu transition layer improved the mechanical integrity of Cu-based coating architectures, shifting the failure location away from the CFRP/coating interface in Zn-based systems. Microstructural analysis confirmed continuous multilayer coatings with effective interparticle bonding, demonstrating the suitability of combining AWS compliant interlayers with HPCS functional topcoats. These findings demonstrate that optimized multilayer architectures—combining compliant Zn-based interlayers, Zn/Cu transition layers, and Cu topcoats—provide a robust and scalable approach for CFRP metallization, enhancing interfacial bonding, mechanical integrity, and electrical functionality, and highlighting their potential for future aerospace lightning strike protection applications.