Cure monitoring of matrix resin with high-frequency electromagnetic wave transmission line

A new monitoring method for the curing process of matrix resin is proposed. In this method, a high-frequency electromagnetic wave transmission line is constructed inside or on the surface of a material and changes in the characteristics of the line during the curing process are measured. The use of a high-frequency electromagnetic wave mainly aims at getting information on the position of the discontinuity or distribution of material properties, making use of its short wavelength. As the first step of the investigations, an experimental setup of a microstrip line and a parallel-wire line was constructed, and changes in the frequency characteristics of reflectance from each of the lines were monitored during the curing of epoxy resin between the pair of conductors of the line. Changes in the characteristics when the resin is partly filled were also investigated to examine the possibility of detecting local distributions or discontinuities. The experimental results are successfully explained by theoretical calculations. Results obtained in this study suggest the potential of the transmission line of a high-frequency electromagnetic wave as a tool for in-situ monitoring of curing and other properties.