At the present time, carbon fiber tanks are very expensive, with the high pressure vessel industry standard Toray T700 carbon fiber costing between $20 and $50 per kilogram alone. At this high price, the carbon fiber currently comprises as much as 75% of the overall tank cost and is a major roadblock on the path to commercialization. To make hydrogen fuel cells in early market and light-duty vehicles commercially viable, the cost of carbon fiber or the amount of carbon fiber used must be significantly reduced. One effective way to lower the weight, thus decreasing the carbon fiber usage and lowering the cost, of a CFRP tank is to improve the mechanical properties of the CFRP composite resin matrix using nano-reinforcement. Using the resin matrix itself as a source of composite strength, along with the carbon fiber reinforcement, results in a tank that requires less carbon fiber material. This solution decreases the weight of the tank while preserving or even increasing its performance. The overall goal of this two phase program is to improve the mechanical properties of the epoxy matrix ( & gt;60% improvement in strength and & gt;100% improvement in modulus) utilizing NH2- functionalized CNT reinforcement. The goal is to reduce the weight of the CFRP portion of hydrogen fuel tanks by 40% while maintaining or increasing the performance when compared to hydrogen fuel tanks at standard weight without CNT reinforcement. The ultimate target is to significantly lower the expense of the carbon fiber (~40% cost reduction). The reduced weight of the hydrogen fuel tanks will make this possible. In the DOE SBIR Phase I program, our approach was successful in that we achieved a 52% improvement in compression strength and a 63% improvement in compression modulus in the epoxy matrix using NH2-functionalized CNTs. Tensile and flexural properties were also significantly improved. We were not able to achieve a hydrogen fuel tank with significantly lightened weight. Due to the increased viscosity of the CNT reinforced epoxy resin compared with the neat epoxy, the CNT reinforced epoxy resin did not penetrate and adhere to the carbon fibers during the filament winding portion of the tank fabrication process. But we firmly believe that this issue can be resolved in the Phase II program. We used a surfactant to lower the viscosity of the CNT reinforced epoxy and checked the mechanical performance of the CFRP ring. Very promising results were achieved. In the Phase II program, we will further improve the mechanical properties of the CNT reinforced epoxy, modify the process for fabricating the CNT reinforced tanks with reduced weight based on both 5,000 and 10,000 psi pressures and perform more sophisticated testing on then. Most importantly, the CNT reinforced epoxy resin with significantly improved mechanical properties has the possibility to revolutionize the entire composite industry. With substantially increased strength properties using CNT reinforcement, the end product will be significantly stronger and lighter than conventional CFRP/GFRP composites currently used in many applications including hydrogen fuel tanks. Customers in all industries will be able to make their existing products, using their existing production methods, substantially lighter, stronger, faster, and consequently, greener.
