Pre-exponential factor and activation energy of electrical conductivity in polyester resin/carbon fibre composites

The electrical behaviour of polyester resin filled with different contents of carbon fibres (0-10 wt.%) has been studied. These composite materials can be classified by their DC conductivity as insulators or semiconductors (below the percolation threshold), or conductors (above the percolation threshold). At the percolation threshold reached at about 1-2 wt.% of the fibres in the resin, a switching effect has been observed. From the Arrhenius temperature dependence of electrical conductivity, the activation energy E and the pre-exponential factor sigma(o) were extrapolated. The linearity of In sigma(o) vs. E confirmed the validity of the Mayer-Neldel rule for the investigated system. (C) 2000 Elsevier Science S.A. All rights reserved.