Modelling TDR response in heterogeneous composite materials

Abstract

The use of Time Domain Reflectometry (TDR) techniques for measuring the moisture content of composite materials is a mature art, but it usually makes assumptions about the homogeneity of the material, since the response of a parallel transmission line to transverse dielectric variation is non-linear. Further, because the electric field distribution depends on the moisture distribution within the material, an analytic solution to the sensitivity distribution in the transverse plane is impracticable, so numerical solutions are required. We describe an integral equation approach to model the response of the TDR system to a heterogeneous dielectric body. Then, in conjunction with a suitable dielectric model of the composite material, the TDR response to moisture content distribution may be quantified.