LAUSR

Abstract The nickel electroplating followed by a further copper electroplating process was conducted on high modulus carbon fibers (HMCFs), and the HMCFs were oxidized in nitric acid prior to the Ni-plating process. Effect of the electroplating process on the microstructure and mechanical properties of HMCFs was investigated. Uniform nickel particles were observed on the surfaces of Ni-plated HMCFs and fiber diameter increased from 5.0 μm to 6.1 μm. With a further Cu-electroplating process, the fiber diameter continued increasing to 7.5 μm. The Ni-plating process resulted in increased surface roughness, whereas the surface RMS and Ra values dropped significantly after the Cu-plating process. Owing to the Ni-plating treatment, the relative content of carbon element on fiber surfaces decreased from 96.54 % to 36.74 %. After a further Cu-plating process, the relative content of Cu element on HMCF surfaces was as high as 54.01 %. The electroplating process resulted in decreased tensile modulus from 415.71 GPa to 407.71 GPa. By contrast, the tensile strength of electroplated HMCFs increased by 1.1 % due to the reduction of fiber defects and stress concentration. Results also showed that both the Ni-plating and Cu-plating process could lead to significant decreases in the values of electrical resistance and resistivity.