Long-life (10-30 years) large space structures are considered by NASA for a number of future earth-orbiting missions. The use of very thin graphite-fiber composites have been considered as structural materials for the fabrication of these structures. A combination of analytical and experimental approaches will be needed to provide a reliable data base on engineering properties of these materials to be used in the design and fabrication of these structures, which will be able to withstand the space environment.