Microwave evaluation of materials
Abstract
Modern microwave tools and measurement techniques show considerable promise for evaluating the electrical and physical properties of materials. These techniques are particularly useful for measuring the dielectric and conductive properties in situ. From these measurements, it is possible to infer many physical parameters such as moisture content, porosity, state of cure or aging, the presence of surface cracks, surface roughness, fiber/filler ratio, bulk fiber orientation, and some constitutent parameters such as graphite. While the wavelength of microwaves (centimeters) limits the spatial resolution required to locate small flaws (deep cracks, voids, etc.), microwaves are ideally suited to measure small variations in density and semiconductive properties of nonmetals. This is best accomplished using coherent techniques which are highly sensitive and capable of measuring the phase as well as the amplitude of the microwave signals being coupled to the test material. Moreover, since microwaves are polarized vector fields, they are highly sensitive to the anisotropy of materials.
- Publication:
-
NASA STI/Recon Technical Report N
- Pub Date:
- May 1985
- Bibcode:
- 1985STIN...8610409K
- Keywords:
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- Aging (Materials);
- Cracks;
- Dielectric Properties;
- Microwaves;
- Moisture Content;
- Amplitudes;
- Mechanical Properties;
- Porosity;
- Surface Roughness;
- Communications and Radar