Modelling the micro-structure of non-uniform conductive non-woven fabrics: Determination of sheet resistance

The plane-wave shielding effectiveness of conductive non-woven fabrics is dominated by the sheet conductance over a wide range of frequencies until the effects of skin depth, and apertures start to influence the performance (typically at 1-10 GHz depending on the areal density). This paper describes models for determining the sheet conductance from knowledge of the type, quantity, orientation and contact resistance of the fibres in the fabricated material. The stochastic nature of these materials, their complexity and local scale variability has been included in the models and correlates well with experimental results. The anisotropic sheet conductance is modelled to within 1% of the measured value in the high shielding orientation and to within 2% in the orthogonal orientation using an inter-fibre contact resistance estimated to be 10 kΩ.