Space environment effects on damping of polymer matrix carbon fiber composites

The effects of the low-Earth-orbit environment on the mechanical properties of some carbon-reinforced polymer matrix composites are reported. Material damping loss factors and glass transition temperatures of control and flight specimens were measured. Flight specimens were attached to the leading edge of the Long Duration Exposure Facility, and control specimens were maintained at the NASA Marshall Space Flight Center. Changes in the glass transition temperatures and damping were due to combined exposure to 1) atomic oxygen, 2) UV radiation, and 3) thermal cycling. High atomic oxygen exposure during the final year of the Long Duration Exposure Facility flight, however, eroded away much of the material that would have been affected by UV radiation. The glass transition temperatures of the flight samples were slightly greater than those of the controls, whereas the material loss factors were nearly the same. From a practical point of view, these changes were not very significant. However, the relaxation data presented herein may be useful for understanding the details of the effects of the space environment on composite materials and may aid researchers in developing composites that maintain their properties for extended periods in the harsh environment of low Earth orbit.