Health Monitoring of Carbon Nanotube (CNT) Enhanced Composites

Composites present additional challenges for inspection due to their heterogeneity and anisotropy, the fact they fail by interacting modes, and since damage often occurs beneath their surface.  Currently successful laboratory non-destructive methods, such as X-ray and C-scans, are impractical for inspection of large integrated structures.  It is clear that new approaches for inspection of composites need to be developed. During the proposed research, Metis Design Corporation (MDC) will collaborate with MIT to resolve these issues by using carbon nanotubes (CNTs). CNTs can offer excellent conducting properties, and MIT has demonstrated the ability to reliably couple CNTs to carbon fibers, greatly enhancing their conductivity. Resistive methods have been investigated previously, however they are hindered by small measurements by conventional fibers and interconnection issues. CNTs have the potential to eliminate both problems by increasing conductivity and offering electrical break-out connections through 3-D leads brought to the surface.  During Phase I, MIT will fabricate prototype CNT enhanced laminates.  Subsequently the specimens will be subject to damage. MDC will evaluate the specimens and formulate algorithms to interpret the data.  At the conclusion of Phase I, MDC will propose an architecture to practically introduce this method into aerospace composite structures. BENEFIT: SHM technologies have the potential for many economic benefits in a broad range of commercial and defense markets.  These systems find utilization within structures ranging from military or civil aircraft to spacecraft and naval vessels.  The first major benefit is that health monitoring eliminates the need for scheduled inspections.  A second major economic benefit is that a continuously monitoring system would allow for the use of the much more efficient condition based maintenance (CBM) design methodology of a structure, otherwise known as need-based repair.  A third benefit is the increased service time of the structure.  Finally, an SHM system could have a significant financial impact if it is able to detect the need for maintenance before a catastrophic failure, potentially saving lives and a costly vehicle.  Airlines that chose to use these systems would be able to reduce the quantity and duration of required inspections, giving them the opportunity cost to capture profit due to more up-time.  Another important aerospace market would be to facilitate launch/no-launch decisions for expendable launch vehicles (ELV), and enable quick turn-around times for reusable launch vehicles (RLV).  One of the key factors to the marketability of this damage detection patch is its versatility, the potential for integration into not just new applications, but existing systems as well.  The first obvious target is the military sector, where one of these systems can reduce the manpower needed for inspection, as well as up to 30% of the maintenance costs.  Additional commercial and space market opportunities exist for the application of reliable damage detection.  These systems can reduce the quantity and duration of airline aircraft inspections, reduce the weight and increase the fuel efficiency of aircraft, and facilitate launch/no-launch decisions for spacecraft.  This will likely be a critical technology for future reusable launch vehicles as well.)