Multi-scale and Multi-functional Self Healing Fiber Reinforced Composites

ABSTRACT: Fiber reinforced composites (FRCs) are attractive structural materials for Air Force applications due to their high strength to weight ratios. Multi-functional self-healing FRCs will advance the state of the art in Air Force applications that either currently use FRCs, or will use FRCs in the future. The multi-functionality, as introduced through dispersed and aligned carbon nanotubes (CNTs), will enable enhanced mechanical and electrical properties not otherwise achievable, and the self-healing property will enable a damaged FRC component to be healed to as-good-as-new condition. We call this the SAN-FRC approach (Self-healing Aligned carbon Nanotubes). Since damage to an FRC structure most frequently occurs at the interface between the matrix and the fiber, the proposed technology addresses this by incorporation of both the self-healing property as well as the CNT multi-functionality at this critical boundary. Building upon our previous work with self-healing FRCs, and in conjunction with our university collaborator"s expertise in fiber processing, we will demonstrate the feasibility of the SAN-FRC approach during Phase I of the program. This will include preliminary evaluation of the self-healing, mechanical, thermal and electrical properties in a bulk composite. In Phase II, we will implement the SAN-FRC approach in the context of a manufacturing process. Life-cycle costs to produce the composite material and prototype airframe structures will be determined in collaboration with a commercial prepreg/FRC manufacturer. Prototype samples will be delivered to the Air Force for testing. BENEFIT: Currently, there is no commercialized technology for self-healing resins for composite materials. Additionally, the current use of CNTs in FRCs is challenging due to the lack of alignment of the CNTs as well as difficulty in dispersing the CNTs in the polymer matrix. The proposed technology solves both of these issues by developing a commercial-ready means of incorporating both the aligned/dispersed CNTs as well as the self-healing agent, where they are needed most to not only self-heal microcrack damage, but also to impart full multi-functionality to the FRC component through enhancement in mechanical, electrical and thermal properties. The developed technology can be implemented in carbon tow, carbon weave, towpreg and prepreg. The technology can be implemented in any Air Force application that uses or will use FRCs. Commercial end-use markets that would benefit from the technology include commercial aircraft, aerospace, automotive, composite overwrapped pressure vessels as used for storage of liquids and fuels, and sporting goods.