Experimental and numerical study of the electrical anisotropy in unidirectional carbon-fiber-reinforced polymer composites

In this paper, unidirectional CFRP composites are considered as an electrical percolation system, which consists of electrically conductive carbon fibers and electrically nonconductive epoxy resin. Due to the contact behavior of the carbon fibers, CFRP has electrical conductivity in the width direction. Resistance measurements using the DC four-probe and the DC six-probe methods are conducted for the unidirectional CFRP specimens with different fiber volume fractions, i.e. different contact conditions. On the basis of the electrical anisotropy level obtained, the correlation between the measured anisotropy and the electrical ineffective length delta(ec), over which a broken fiber recovers its current carrying capacity and a key parameter in electromechanical modeling of CFRP, is shown experimentally. The empirical relationship between the electrical anisotropy and delta(ec) obtained is also reviewed using a numerical calculation method based on the electric circuit theory of Kirchhoff's rule and the Monte Carlo simulation technique.