Abstract
The square-array model with infinite chains of contact is proposed to account for the dependence of electrical properties on frequency and fibre volume fraction in unidirectional carbon-fibre/epoxy-resin composites. The longitudinal AC conductivity, E vector parallel to fibre axis, decreases with increasing frequency due to magnetic flux change from neighbouring fibres and increases linearly with fibre volume fraction due to increment of specific fibre cross section within a volume element. A longitudinal permittivity of nearly unity for the frequency range of 1.7 GHz to 10 GHz, irrespective of fibre volume fraction, suggests that the composites can be considered as good conductors even at higher frequency. The three stages of increment and decrement with increasing frequency for transverse conductivity and permittivity, are ascribed to space charge polarisation. The increment of transverse AC conductivity with fibre volume fraction is ascribed to the increase of conducting channels.
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