Galvanic Current Influencing Interface Deterioration of CFRP Bonded to a Steel Substrate

Abstract

This paper presents an experimental program investigating the effect of galvanic current on the physical and mechanical characteristics of carbon fiber reinforced polymer (CFRP) composite sheets bonded to a steel substrate. Electrochemical reaction is induced by galvanic interaction between anodes (CFRP-steel interface specimens) and cathodes (metallic strips) linked with an electrolyte (a 3.5% sodium chloride solution). Thirty-five test specimens are exposed to various periods of galvanic current from 0 to 72 h until their corrosion rate is converged. Hydrated ferric oxide forms along the CFRP-steel interface with some concentration in the vicinity of its edge, which accompanies a loss in surface area and mass. The electrochemical reaction imposed by the galvanic current exponentially decays with an increase in exposure time. The initiation of corrosion noticeably affects the load-carrying capacity of the CFRP-steel interface, whereas its propagation is not a critical attribute until substantial corrosion damage takes place. CFRP-debonding is the governing failure mode of the interface, irrespective of the degree of galvanic current exposure. The stress-slip behavior of the interface is influenced by the electrochemical reaction and a geometric discontinuity associated with stress singularity. Corrosion-dependent interfacial fracture energy is probabilistically inferred and used for quantifying the degree of interface deterioration subjected to an aggressive corrosion environment.