High resolution MW holographic system for NDT of dielectric materials and details

In recent years, there has been a surge of new applications of composite materials and structures in aerospace industry. The composites have many advantages over traditional metal alloys. They have, as a rule, better strength/weight ratio, withstand to unfavorable weather conditions and aggressive environments. Corrosion also doesn't affect them. Traditional methods of ultrasonic diagnostics are ineffective for porous composites such as polyurethane foam insulation, silicate fiber tiles as well as for honeycomb construction details due to high levels of acoustic wave attenuation in them. In some cases, microwave holographic subsurface radars can be a reasonable alternative to ultrasonic testing. A specially designed test setup, which uses a vector network analyzer for generating and receiving signals, was created. Operational frequency band of the test setup gives opportunity to carry out experiments in a broad range of 10MHz-24 GHz. The setup records complex multi-frequency holograms, for the reconstruction of which the software was developed. A sample of polyurethane foam insulation, which is used for shielding of rocket cryogenic fuel tanks, was tested in the setup. The sample had preliminary produced defects. Comparison of the samples testing results and the defects maps showed that they are in a good coincidence.