Self-Sensing Thermal Management System Using Multifunctional Nano-Enhanced Structures

Thermal control systems on spacecraft rely on accurate temperature measurements at the locations of interest. Today, point measurements are made using thermocouples, thermistors, and RTDs. This research was aimed at calibrating a sensing material that could yield two dimensional temperature field measurements, giving thermal control systems thermal images rather than point measurements. Exfoliated graphite (EG) and latex had previously been developed at the University of Maryland as strain gauges. The temperature response of these gauges without applied strain was studied as the sensing material for these new temperature sensors. The resistance response was calibrated as a function of temperature showing a negative, linear response above room temperature and an exponential relationship below room temperature. After calibration, a grid of twelve sensors was made in a 3 x 3 node pattern. A non-uniform temperature field was applied over the area and the resistance response from each of the twelve sensors was measured. Using the calibration data found previously, the resistance changes of each sensor were converted into temperatures. A matlab program took these temperature values and created contour plots to show how the calculated temperatures related to the IR camera image of the surface in real time. This research proved that a grid of these nano-enhanced conductive composite sensors were able to measure temperatures and produce thermal images from their responses. These generated thermal images were compared to IR images taken during the experiments and proved that the sensor grids produced thermal images equal to the theoretical images within two degrees Celsius. Although the sensors successfully measure temperature, future work includes studying alternative polymer matrices to be used other than latex. The polymer should be able to be integrated into 3D printing machines so that these sensors can one day be printed directly into structures.