Description: The objective of this work is to determine the optimal process for manufacturing lightweight linerless cryogenic storage tanks using ionic liquid epoxy composite material that can compete with metallic tanks currently in use. Ionic liquids, because of their unique properties such as low volatility, low flammability, and flexibility of chemical design are showing promise as the next generation of chemical reagents. Mechanical and chemical testing to date has shown that this IL epoxy monomer, when cured with a commercial aromatic diamine curing agent, yields a polymer resin with high tensile strength, excellent bond strength to aluminum and steel, high toughness, low CTE, and low moisture permeability. Performance comparisons of the ILE to several commercial epoxies showed the ILE had superior tensile and bond strengths. Of particular importance is that these properties of the ILE were even better at cryogenic temperatures because of the low crystallinity inherent in the polymer as a consequence of the chemical nature of ionic liquids. In this Phase I effort, a battery of tests will be carried out at room and liquid nitrogen temperatures on coupons prepared preferably on a filament winder using the wet winding technique. Hand layup may also be used to make small defect-free samples. Samples for tensile, lap-shear and bend (for interlaminar shear strength) will be cut from these. Potholing or surface degradation, microcracking and delamination will be reported and quantified if found.

Benefits: While the US Department of Transportation doesn't currently have regulations that specify or allow the use of composite tanks for liquid hydrogen transport, it is anticipated that the increasing interest in hydrogen as an alternative fuel will force the need for such regulations and create a rapidly emerging market for composite storage vessels. The outstanding performance of the ILE as an adhesive coupled with the fact that it uses no volatile organic compounds makes it an ideal material for a number of "green" applications where off gassing is a consideration.

There is a broad range of space flight applications for this technology. It has immediate application to current spacecraft lift vehicles as a replacement for heavier materials by reducing propulsion system mass. There is also an immediate application for storage tanks for cryogenics like oxygen or helium used for life support, fuel cells or pressurization systems on earth as well as in space. This IL epoxy adhesive can be further developed to be used for mounting optics in space flight hardware, as well as general adhesive use for space flight applications and possibly during EVA activities.