DC ELECTRICAL-CONDUCTION PHENOMENA BETWEEN 2 NONCONTACTING STAINLESS-STEEL FIBERS IN A POLYCARBONATE MATRIX

Model two-fibre devices have been constructed to simulate the local electrical environment between neighbouring fibres in stainless steel fibre polycarbonate composites. The voltagecurrent characteristics of the device have been studied as a function of the shortest distance (gap length) between the fibres, arranged in T-configurations. From the device behaviour it is concluded that to explain the observed levels of resistivity in bulk composites (as low as a few ohms centimetres for 1% volume fraction of metal) gap levels must be <1 nm. Whilst the device resistance for larger gaps of several micrometres is too large to explain bulk resistivities of a few ohms centimetres in composites, it is nevertheless six orders of magnitude lower than one would expect if tabulated bulk resistivities of polycarbonate (2 × 106 Ωcm) obtained in the gap between fibres. Furthermore the lowest experimental estimate of the dielectric strength of the polycarbonate in the gaps, exceeds by a factor of ten or more the tabulated value for bulk polycarbonate. In the conclusion some tentative suggestions on the origin of these device 'size effects' are presented. This involves consideration of the length and orientation of polymer chains in relation to the gaps and cross-linking effects. © 1990 Chapman and Hall Ltd.