POROSITY LEVEL ESTIMATION IN POLYMER COMPOSITES USING MICROWAVES

The ability of microwaves to monitor variations in porosity level of c omposite samples is studied. Measurements of several carefully prepare d samples with different air volume fractions are performed at the fre quency range of 8.2-18 GHz, The measurement results indicated that the re 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 measure d results. This model may be used to closely predict Me amount of air content from measured dielectric properties. Changes in clustered (loc al) porosity are studied experimentally as well. Microwave scan of spe cially prepared samples with about 5 percent change in air content (lo cal porosity variation) are also presented.