Time - Domain - Reflectometry Cure Sensors

Advances in high performance polymer composites require precise methods of process monitor and control. Techniques using embedded sensors for in-situ monitoring provide such capability. A new method based on real-time monitoring of small molecule rotation in the developing matrix is proposed. The method uses a transient dielectric measurement, Time-Domain-Reflectometry Dielectric Spectroscopy, to capture a broad rotational spectrum at once. Transient response is sampled by embedded electrode sensors and converted to microwave frequency spectra by Laplace transform; variations in converted spectra are in turn related to cure. The proposed method offers advantages in that 1) the electrode sensors are simple and easily embedded in the process material, 2) the small-molecule mechanism monitors absolute levels of cure, and 3) the transient measurement technique tracks cure evolution at high rates of speed. Expected results will be the development of electrode sensors suitable for in-situ monitoring, identification and tracking of small molecule activity in representative epoxy systems, and an initial correlation between this activity and rheological and mechanical properties. the work draws on much experience in our laboratory in dielectric process monitoring, and on new work involving transient dielectric measurement in high conductivity liquids and gels.