Prediction of failure thermal cycles in graphite/epoxy composite materials under simulated low earth orbit environments

Abstract

In order to evaluate the changes in the mechanical properties, mass and coefficient of thermal expansion of composites in space, graphite/epoxy composite specimens were exposed to simulated low earth orbit (LEO) environmental conditions including ultraviolet radiation, thermal cycling and high vacuum. Surface morphology was investigated by using a scanning electron microscope, and outgassed products were analyzed with a quadrupole mass spectrometer. The failure cycle of composite laminates exposed to the attack of LEO environmental factors was predicted by using four modified failure criteria. The modified failure criteria were expressed as a function of stresses as well as thermal cycles.