Research on Improving Fuel Containment Performance of Composite Fuel Tanks

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In order to construct the cryogenic fuel tanks of launch vehicles by fully utilizing the advanced composite materials, this research project was aimed to look into the possibilities of improving the fuel containment performance of the tanks. As the string of damages could function as the path of fuel leakage, the quantitative relationship between transverse cracks and permeation was obtained based on the semi-analytical model. The transverse cracks were thus found to be the essential cause of the leakage. The prevention of the leakage is dependent on the existence of intact or damage-free plies in the laminate. The formation of transverse cracks in contiguous plies was also thoroughly investigated both experimentally and analytically from this standpoint.To further reduce the robustness of the fuel tanks against permeation, carbon nanotubes were employed as an additive to the resins of the composites, both mechanically increasing the toughness and physically reducing the diffusivity through the resin. The mechanical as well as thermal and electrical properties were looked into for the resins dispersed with nanotubes at various weight content. Epoxy and polyetherimide were used as basic resins. The contribution of the nanotubes to the stiffness improvement was larger for polyetherimide resin, whereas the increase in electrical conductivity was higher for the epoxy, showing the complex contribution of the nanotubes to the different properties.The results of the present project is summarized as the collection of reviewed papers together with the conference papers, published in the past three years.