Time-domain terahertz reflection imaging is a proven NDE technology for imaging sub-surface features, flaws, and defects within space flight structures such as thermal protection systems (ablative resin honeycomb, TUFI, SOFI), inflatable space habitats, composite overwrap pressure vessels, radomes, and other dielectric components. THz pulses (0.1 to 3 THz) penetrates these materials, and can be used to generate sub-surface images. THz NDE can detect voids, disbonds, and damage such as tearing and micro-meteorite impact. Material examples include Kevlar, Zylon, and other non-conductive polymer matrix composites. Differential THz imaging should improve the detectability of defects in each of these applications.
Time-domain terahertz gages are used in industry to measure the thickness of multi-layer sheet materials such as plastic film, insulation, foam sheets, roofing, paper, and other similar products that are extruded in presses. THz gages are used to measure the thickness of aerospace coatings, when dry or wet. The proposed differential imaging method and shearographic loading techniques should enhance the detectability of interfaces and delaminations in the manufacturing of these materials. THz instrumentation has significant potential in the research and development, government, and industrial markets for use in on-line and off-line inspection, communications, and test and measurement.