POROSITY LEVEL ESTIMATION IN POLYMER COMPOSITES USING MICROWAVES

The ability of microwaves to monitor variations in porosity level of composite samples is studied. Measurements of several carefully prepared samples with different air volume fractions are performed at the frequency range of 8.2-18 GHz, The measurement results indicated that there is an excellent sensitivity to small differences in porosity level. A two-phase mixing model used for predicting Me dielectric properties as a function of porosity level shows good agreement with the measured results. This model may be used to closely predict Me amount of air content from measured dielectric properties. Changes in clustered (local) porosity are studied experimentally as well. Microwave scan of specially prepared samples with about 5 percent change in air content (local porosity variation) are also presented.