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

ABSTRACT: Due to their high strength to weight ratio, fiber reinforced composites (FRCs) are attractive structural materials for Air Force applications. Multi-functional self-healing FRCs will be beneficial in applications that either currently use FRCs, or will use them in the future. The introduction of high loading levels of 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). Damage to an FRC structure most frequently occurs at the interface between the matrix and the fiber; the proposed technology addresses this by delivering a self-healing function, as well as CNT reinforcement, at this critical boundary. Building upon the proof of concept demonstrated during Phase I, we will implement this technology into FRCs within the context of a manufacturing process during the Phase II effort. To accomplish the goals of the Phase II program, we have put together a team that includes manufacturers and a DoD prime contractor, in addition to our university partner. This will allow us to further develop the technology with a focus on manufacturing and end-use applications, from both a DoD and a commercial perspective. Life-cycle costs to produce the composite material and prototype structures will be determined in collaboration with a commercial prepreg/FRC manufacturer. Prototype samples will be delivered to the Air Force for testing. We expect the TRL to be 5 at the end of the Phase II program. Future R & D will include additional long term testing and validation, which will help commercialization and full implementation. 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 both the lack of alignment of the CNTs, as well as the difficulty in dispersing them in the polymer matrix, especially in high concentrations. The proposed technology solves these issues by delivering a commercial-ready means of incorporating both the aligned/dispersed CNTs and the self-healing agent to the matrix and fiber interface, where they are needed the most. This allows self-healing of microcrack damage, as well as enhancement in mechanical, electrical and thermal properties. The developed technology can be implemented in carbon tow, carbon weave, towpreg and prepreg. 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.