SBIR-STTR Award

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.

Keywords:
Terahertz, Non Destructive Evaluation, Aircraft Maintainability, Rf Material Systems, Point Inspection Tool, Cure Monitoring, Advanced Sensor, Dielect

We propose to develop and test a prototype TD-THz system and method for the non-contact, rapid, in-process cure monitoring of specialty material coatings. The instrumentation will determine the thickness and cure state both “dry” and “wet” coatings and predict final thickness from “wet” measurements. The system will consist of a rack mounted TD-THz control unit which is connected to a miniature TD-THz reflection sensor via a flexible umbilical mounted onto a robot arm within a paint booth. The fiber optic coupled TD-THz technology is highly suitable, as the sensors are small, light weight, and freely positionable. In-process monitoring is desirable when tight thickness tolerances are required, but difficult, because the coating is uncured. By measuring in-process, the application can be adjusted, and waiting to cure and sanding can be avoided. The TD-THz thickness and cure state measurement offers several advantages

Keywords:
Terahertz, Non Destructive Evaluation, Aircraft Maintainability, Rf Material Systems, Point Inspection Tool, Cure Monitoring, Advanced Sensor, Dielect