Transverse electrical conductivity characterisation for tape-based thermoplastic composites

Induction welding is a promising assembly technology for joining carbon fibre reinforced thermoplastic composites. This method relies on inducing eddy currents in the carbon fibre network, with the resulting heat contingent on the part’s electrical conductivity. Accurately describing the conductivity is key to predictive numerical simulations, necessary for further industrialisation of the welding process. This study specifically concentrates on the efficient experimental characterisation of in-plane and through-thickness transverse electrical conductivities in unidirectionally reinforced carbon fibre- peak composites, using the six-probe method. The investigation addresses the stochastic nature of the conductive paths within the fibre network by considering specimen dimensions, spatial variations and the non-uniformity of the current density distribution. Two material systems were assessed via both the classical six-probe method, as well as two novel thin variations on the methodology. The results are consistent across methods, with the newly introduced thin configurations proving particularly effective for accurately characterising intrinsic ply-scale electrical conductivities rather than laminate-averaged behaviour.