The National Aeronautics and Space Administration (NASA) Space Shuttle is the only launch vehicle in service today with reusable components. To address the issues of an aging Space Shuttle fleet, and to advance key technologies associated with increased performance, NASA has initiated the Space Launch Initiative (SLI) program. One of the key performance advances identified for next-generation reusable launch vehicles (RLV's) is the reduction in structural weight through the use of advanced materials and manufacturing methods. This reduction in structural weight must be tempered against the safety and reliability criteria associated with damage tolerance, and lifetime durability.

No abstract

This paper presents experimental methods and results of an ongoing study of the correlation between damage state and hydrogen gas permeability of laminated composite materials under mechanical strains and thermal loads. A specimen made from IM-7/977-2 composite material has been mechanically cycled at room temperature to induce microcrack damage. Crack density and tensile modulus were observed as functions of number of cycles. Damage development was found to occur most quickly in the off-axis plies near the outside of the laminate. Permeability measurements were made after 170,000 cycles and 430,000 cycles. Leak rate was found to depend on applied mechanical strain, crack density, and test temperature.

No abstract

No abstract