I-Corps: Development of Self-healing, Fiber-reinforced Composites

North Carolina State University, Raleigh NC

Investigators

Abstract

The broader impact/commercial potential of this I-Corps project is the development of self-healing fiber-reinforced composites (FRC). The proposed technology may be used to autonomously repair delamination damage during service, thereby enhancing the durability and longevity of modern structures. Globally, FRC represent one of the largest and fastest growing sectors of advanced materials technology. This growth stems from the numerous high-performance applications for FRC in a broad range of industries that include aerospace, defense, green energy, automotive, marine, infrastructure and electronics. Many of the composite structures used in the highest value applications are multi-layer laminates that are exposed to repeated stresses over multiple years (up to 30) of service. The proposed self-healing composite is specifically aimed at preventing premature failure in these laminated composite structures and extending service life. In addition, self-healing FRC also provide a more sustainable pathway that prolongs service life and enhances resilience and durability, making such materials particularly attractive in composite industries where maintenance and replacement and associated downtime are costly. Industries such as Aerospace also may benefit from enhanced safety, where end-users have reported issues with delamination-susceptible parts including rotorcraft blades and other components featuring ply-drops and fastener holes where stress concentrations arise. This I-Corps project is based on the development of a self-healing fiber-reinforced composites (FRC) platform that achieves in situ self-healing via thermal re-mending. The proposed approach relies on mendable thermoplastic (TP) that is 3D-printed directly onto woven fiber reinforcement and co-laminated with carbon-based resistive heaters. The patterned TP exhibits high melt-flow and self-pressurization for confined micro-crack delivery at temperatures below the glass-transition of the composite thermoset matrix. Rapid (minutes-scale) in situ thermal re-mending is accomplished via resistive heating. Printing TP directly on the reinforcement increases interfacial bonding, resulting in a cohesive failure through the thermoplastic interphase. Test results show a four-fold increase in mode-I fracture toughness over a plain composite, and a consistent self-healing performance (up to 100%) via dynamic re-bonding for sustained cycle counts (100+). The prolonged recovery made possible via this proposed in situ thermal re-mending strategy represents an order of magnitude leap in self-healing repeatability compared to prior technologies. In addition, the composite augmentations for self-healing preserve mechanical properties and are compatible with existing manufacturing processes, both of which are critical for eventual commercialization. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.