Smart tooling with integrated time domain reflectometry sensing line for non-invasive flow and cure monitoring during composites manufacturing

An electrical transmission line integrated into composite tooling has been developed to facilitate non-contact multipoint flow and cure monitoring during vacuum assisted resin transfer molding processing. The sensor is made of conductive aramid (Kevlar®) fibers and is an integral part of the glass fiber composite tooling. Electrostatic simulations in COMSOL® have been performed to optimize the wire spacing maximizing the sensitivity of the electric time domain reflectometry measurements. Tooling with integrated wires placed with optimal spacing has been fabricated. TDR flow monitoring experiments with the integrated sensor have been conducted and compared visually using digital image processing. TDR data obtained from the same sensor also enables measurement of the resin cure state. Fast and slow curing resin systems have been studied using the transmission line integrated tooling and differential scanning calorimetry experiments have been performed to validate the cure measurements obtained from TDR. Major benefits of the sensor implementation include elimination of ingress/egress issues associated with standard sensor integration into composite tooling as well as reduced maintenance of the non-contact solution.