Microwave determination of the mechanical strains in glass-reinforced plastic articles

A review of microwave testing of glass fibre-reinforced polymer composites

“…When mechanical loads are applied, the fibres are mutually displaced, which could lead to changes in the complex permittivity of the composite. Kovalev et al [74] studied the effect of the mechanical strains and found that there was a linear relationship between the deformation and the dielectric constant. It was also possible to obtain the strain distribution by measuring the dielectric constant with the electric field in different directions with respect to fibre orientation.…”