THz Multi-layer Coating Thickness Sensor

PSI proposes to develop a multi-layer coating thickness sensor to be used for aircraft maintenance. This sensor will use time domain THz technology to determine the thickness of coatings above an electrically conductive coating based on the timing of reflected pulses from the interfaces between the coatings. In the Phase I effort, we will characterize the THz absorption and index of refraction of the coatings and determine the best strategy for measuring the thicknesses of the two coatings above the conductive layer. This characterization effort will be followed with a laboratory demonstration of a multi-layer coating thickness measurement. Signal processing strategies for extraction of the coating thickness will also be pursued. Finally, a preliminary design of the Phase II prototype will be completed, and vendors for critical components will be identified. The proposed research is poised to take advantage of PSI’s previous efforts to develop a real-time paint thickness sensor for marine paints. In the Phase II program, a prototype sensor optimized specifically for the inspection needs of the Air Force will be constructed and the performance of this sensor will be evaluated. BENEFIT: This program will generate a sensor capable of measuring coating thicknesses in multi-layer aircraft coatings. This sensor will be used to calibrate tools that are used to inspect the integrity of conductive coatings used on aircraft. This sensor will enable Air Force personnel to reliably inspect conductive aircraft coatings. We anticipate commercial applications to include a variety of NDE (non-destructive evaluation) requirements in coated items.