In-Process Cure Monitoring of Specialty Material Coatings

We propose to demonstrate the feasibility of a fiber optic coupled pulsed time domain terahertz (THz or T-Ray) instrument to measure aircraft specialty coatings during in-process curing. The method employed will be capable of measuring the complex dielectric constant and thickness of the coating during and after the curing process. We will experimentally investigate a polyurethane coating, and develop a method to predict the post-cure dielectric properties from the pre-cure measurements. The proposed method will be able to measure these properties on a wide variety of coating and paints. The T-Ray measurement process is suitable for both composite and metallic substrates. The reflection T-Ray sensor will have non-contact operation, with working distances adjustable from less than 1 cm up to 100 cm. Measurement will be real time, with waveforms acquired at rates up to 100 Hz. In phase II, we will construct an on-line capable prototype T-Ray coating measurement system, based on specifications determined in the Phase I project. The system will be tested under realistic conditions and delivered to the Air Force for field-testing. The proposed T-Ray reflection sensor will be freely positional, suited for hand-held use or mounted on a robot.