Investigations on the Use of Near-Field Measurements to Determine the Effective Conductivity of Advanced Composite Materials

A technique is described whereby the effective conductivity of composite samples is determined using magnetic near-field insertion loss measurements. The measurement does not require electrical contact with the material under test and is therefore ideal for materials processed using advanced composite material manufacturing techniques where nonconductive matrix materials are employed. The material's conductivity, measured using this technique, is used to analytically determine the plane wave response of cylindrical samples. These analytical results agree well with the plane wave shielding experiments, which are performed in transverse electromagnetic (TEM) cells. The measurements are performed at frequencies below 150 MHz because of limitations in dynamic range. (MM)