Permittivity of woven fabrics: A comparison of dielectric formulas for air-fiber mixture

The dielectric properties of textile fabrics are becoming more important with respect to applications such as electrostatic discharge, electromagnetic shielding, fabricreinforced composites for electrical and electronic applications. The relation between the permittivity of the fiber material and that of the air-fiber mixture in a fabric form belongs to a more general problem of dielectric mixtures which has been studied for more than 100 years. This paper reviews many such dielectric mixture formulas available today and applies them for the case of a woven fabric made from monofilament yarns of high density polyethylene. At the low fiber volume fraction which is typical for any woven fabric, the dispersion of values given by different mixing equations lies between 2.028 and 2.400. An extrapolation technique using a quadratic equation also gives a reasonable value which falls in the above range.