Recently, graphite/epoxy composite materials are quite common in aerospace structures. In order to study the change of physical and mechanical properties of composite materials under space environment, HFG CU-125NS graphite/epoxy laminate specimens were exposed to the simulated low earth orbit(LEO) condition inside a thermal-vacuum chamber with high vacuum($10^{-5}~10^{-6}Torr$), UV(<200nm wavelength radiation) and thermal cycling environments. The exposed specimens were examined in their surface morphology and tested the change of coefficient of thermal expansion and mechanical properties after 40, 80, 200 and 400 thermal cycles.
The matrix-loss was observed at the surface of specimens aged 200 and 400 cycles. The coefficients of thermal expansion of composite materials decreased with the thermal cycle. As a whole, there were no catastrophic decrease of stiffness and strength of composite materials. But the compressive and flexural strength decreased more than other properties with increase of aging time.