Multifunctional Structural Power and Energy Composites for U.S. Army Applications

Abstract : Many U.S. Army systems depends on the efficient use of material mass and volume. Many components on these systems are often dedicated to power generation and energy storage. Examples include next-generation ground vehicles and individual soldiers, whose sensing and communication equipment requires both continuous and burst power. Many of these systems also include a significant amount of structural and/or armor materials. Therefore, important system-level reductions in mass and volume are possible by creating multifunctional materials that simultaneously offer both power generation or energy storage capabilities with structural or armor properties. Three candidate multifunctional materials are under investigation. First, structural fuel cells have been fabricated by creating skin-core composite structures. In these fuel cells, the skins are composed of thin, glass fiber or carbon fiber reinforced composite laminates. The core consists of layers of open-cell metal foam with a Nafion(R)-based membrane electrode assembly interlayer. This core generates power when hydrogen and oxygen sources are circulated through the porous foam layers. Simultaneously, the high shear and compressive stiffness of the core transfers loads efficiently to the skins, resulting in a structure with high specific stiffness and strength. Secondly, structural lithium-ion batteries are being designed by formulating ion-conductive polymer electrolytes with continuous fiber reinforcement. The electrolytes are designed to balance structural and ion-conduction properties, through the use of functionalized structural polymers, block copolymers, or microscale mixtures of conductive and structural materials. Finally, electroded surfaces have been integrated into continuous fiber reinforced polymeric composites, to create structural capacitors.