In Situ Process Monitoring of Carbon Nanotube/Glass Fiber/Polyester Multiscale Hybrid Composites

Abstract

There are many technical challenges associated with processing of multiscale hybrid composites, including incomplete resin infusion, improper resin cure, and non-uniform properties due to nanomaterial filtration. We introduce effective methods to monitor in situ resin flow, cure, and nanomaterial filtration in carbon nanotube(CNT)/glass fiber/unsaturated polyester composites. The key underlying concept is to monitor the change in percolated CNT conductive network subjected to resin infusion, cure progression, and CNT filtration. Two cases were considered: (1) glass fiber fabric spray-coated with CNTs prior to neat resin infusion; and (2) CNTs pre- dispersed in resin prior to infusion into untreated glass fibers. In the case of CNT-coated glass fibers, it was demonstrated that the resistance of as-coated CNT conductive network can be used to identify critical events that take place during the entire composite processing cycle, including the onset of crosslinking and gel point of resin, as well as in-plane and through-thickness resin flow. In addition, it was demonstrated that CNT filtration can be detected through the change in electrical resistance along the resin flow direction, and the gradient in part quality can be predicted. We have demonstrated simple yet effective methods to monitor the manufacturing processes and predict the final part quality of multiscale hybrid composites, which can be integrated into the existing processes with minimal modifications.