Complex permittivity measurements of curing epoxy resin in glass-fibre reinforced composite

In this work a novel concept for cure monitoring of epoxy resin in glass fibre reinforced composite material by evaluating its dielectric properties is presented. Two dielectric mixing formulas are introduced and discussed. An algorithms is implemented for each formula to separate the complex permittivity of the epoxy resin and the glass-fibre textile from the permittivity measurements of the whole composite material. Both implementations include an iterative adaption of the assumed fibre volume fraction to the actual volume. The algorithms are tested and verified with free-space transmission measurements at 24 GHz.