Fully Integrated Flexible Dielectric Monitoring Sensor System for Real-Time In Situ Prediction of the Degree of Cure and Glass Transition Temperature of an Epoxy Resin

Flexible dielectric sensors received significant interest for real-time in situ cure monitoring of polymeric composites over the past decade. Currently, the state-of-the-art dielectric sensors mainly focus on detecting the distinct stages of the polymeric composite curing process. While low-cost and quantitative monitoring of the thermal, mechanical, and chemical properties of the materials during the cure is of great interest, to date, such a sensor system has not been realized because the existing devices excessively depend on external instrumentations, combined with a lack of an embedded reliable data processing module. Here, a fully integrated dielectric monitoring sensor system (DMS) incorporating dielectric and temperature sensors is developed, capable of monitoring in real-time the temperature, the degree of cure, and the glass transition temperature (T-g) of polymeric composites. An independent characterization of the cure kinetics was performed using differential scanning calorimetry and Raman spectroscopy. These data enabled associating the main physical and chemical transformations in the polymeric materials with particular features observed in the dielectric measurements. We demonstrate the accurate estimation of the degree of cure and T-g of an epoxy resin. The proposed system shows the potential for a new generation of intelligent manufacturing technology of composite materials.