Challenges associated with damage tolerance in polymer matrix composites must be successfully addressed in order to ensure highly reliable structures with significant weight savings. Self-healing materials provide a viable means to surmount damage tolerance concerns, thereby allowing for the realization of the mass reduction such structures have promised but not yet achieved. Introduction of multifunctional properties into self-healing composites can further extend their usefulness. This study examines the incorporation of carbon nanotubes into a self-healing composite in order to achieve this. Composite panels were fabricated with carbon fibers, a bismaleimide tetrafuran (2MEP4F) polymer resin, and various carbon nanotube materials. The composites exhibit enhancement in electrical, mechanical, and thermal properties. The healing mechanism is a thermally activated reversible polymerization of the 2MEP4F resin. The proposed method of heating exploits the enhanced microwave absorption inherent to carbon nanotubes to provide the thermal energy required for the reversible polymerization. Microwave testing demonstrated that the heating efficiency is increased, allowing uniform heating to the required temperature for polymer healing. Impacted composites show localized heating at the damage site, which implies that microwave heating can also be used as a means for damage detection and potential structural health monitoring. 1. Introduction The National Aeronautics and Space Administration (NASA) is currently evaluating composite materials for primary and secondary structures in habitat modules, crew vehicles, pressure vessels, and other potential applications. Lighter-weight materials with high specific strength can lead to drastic reductions in uptake mass, resulting in more cost effective space exploration. Such materials can have similar benefits in commercial applications such as aircrafts, vehicles, and wind turbine blades, as well as a variety of infrastructural applications. As such they are of great interest not only to NASA but also to the commercial sector. Polymer matrix composites have attracted much attention due to their relatively high strength, light weight, and low cost. An integral design concern, however, is that of damage tolerance. Nearly imperceptible cracks may form upon impact which, while being microscopic, may have drastic effects on structural integrity. As a result, structural composites are designed to be thicker and heavier than would otherwise be required, thus negating some of the weight savings they promise. One way to
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