TOUGHENED GRAPHITE-EPOXY COMPOSITES EXPOSED IN NEAR-EARTH ORBIT FOR 5.8 YEARS

This experiment was designed to measure the effect of near-Earth space exposure on three mechanical properties of specially toughened unidirectional T300/5208 graphite-epoxy cross-ply composite materials. The properties measured are fracture toughness, elastic modulus, and strength. Six toughness specimens and nine tensile specimens were mounted on an external frame during the 5.8-y orbit of the Long Duration Exposure Facility. Three identical sets of specimens were manufactured at the outset: the flight set, a zero-time nonflight set, and a total-time nonflight set. Results indicate that with proper protection from solar exposure and atomic-oxygen degradation, toughened graphite-epoxy composites can provide useful structural service in near-Earth orbit for at least five years.