Research on Electric Conductivity of Thermo-plastic Composites Based on Eddy Current Loss

Thermoplastic composites has attracted extensive attention in industrial process with excellent properties. As one of the most important parameters, electric conductivity is difficult to detect due to its inhomogeneity and anisotropy. In this paper, a novel method for measuring volume electric conductivity of composites based on eddy current loss has been introduced by using both experimental and numerical approaches. Initially, the eddy current loss and equivalent volume conductivity under different magnetic flux density are presented by analyzing voltage and current acquired in a designed air-gapless reactor under 500 Hz sinusoidal excitation with variety amplitudes. Then, to verify the measurement method and determine the influence of different materials on the eddy current loss, a 3-D electromagnetic model of the experimental devices is built and three cases with different materials are calculated. The parameters including eddy current loss and magnetic flux density are presented. The mechanism underlying the influence of different conductivity on the measuring model is analyzed according to the confidents and eddy current loss. Results show that the ratio of eddy current loss to the square of magnetic flux density is linear. The formula of equivalent volume conductivity needs to be revised by multiplying certain coefficients for high conductivity due to the eddy current effect on the detection coil. It is reasonable that magnetic flux density rang is set in 0.2~0.8T during measurement.