10d. Composite Overwrapped Pressure Vessel Monitoring by Electrical Resistance

Composite overwrapped pressure vessels are commonly employed in various industries, including in the automotive industry, to store and transport gases. With increased sales of hydrogen fuel cell cars that rely on composite overwrapped pressure vessels for hydrogen storage, tank safety has become a major concern due to their high energy capacity. Recent rocket explosions are a prominent example of how composite overwrapped pressure vessels may catastrophically fail. Continuous structural health monitoring solutions are sought to assure the safety of composite overwrapped pressure vessel operation. To sense and record abnormalities in mechanical strain and to mitigate the risks associated with structural failures of these pressure vessels, a new conductive synthetic fiber-based strain monitoring technology based on proven technology will be developed for this application. Synthetic smart fibers will be embedded in the composite overwrap to act as in situ pressure and strain sensors inside the host structure. The strain sensing smart fiber is a co-extruded, bi- component polymer filament with a dielectric sheath layer and an electrically conductive core layer. Pressure and strain sensing is achieved by monitoring the changes to the filament’s resistive and reactive properties due to mechanical deformation under applied strain. This integrated pressure monitoring system will provide continuous on-line monitoring of structural conditions for the vessel, improving its safe operational lifespan. The Phase I development will focus on demonstrating the feasibility of the system, including strain sensing fibers, their connectorization, an electronic reader, and an analysis algorithm. We will embed the smart fibers into different layers of the composite overwrap and test the sensors’ responses to different modes of failure (tensile and impact testing). An electronic reader will also be developed for real-time recording of the change in resistance of the embedded strain sensing fibers. The data will be analyzed for abnormalities through the use of learning algorithms and the results will be used for triggering a vessel failure warning.The combination of smart fibers, capable of being integrated into carbon overwraps, and low-power reader electronics will provide in-situ structural health monitoring for automotive hydrogen fuel cells, increasing their safety of operation and potentially reducing cost and weight due to improved safety margins. Competitive advantages include the reduced cost of the smart fibers compared with existing structural health monitoring technology, as well as the ability to seamlessly integrate into the composite structure.