Accelerated Aging of the Thermal Expansion of Unidirectional Graphite/Epoxy Composites by Thermal Fatigue

The longitudinal coefficient of thermal expansion (α 1 ) of unidirectional T300/934 and AS/3501-5A graphite/epoxy (Gr/Ep) composite changes within a thousand thermal cycles at ranges greater than 210 o C. A phenomenological model is developed to extrapolate α 1 to a smaller thermal range (<100 o C) and longer duration (2×10 5 cycles) typical of service in low earth orbit. Factors affecting fiber/matrix interface cracking are considered, and the utility of calculating α 1 from an «effective» fiber volume fraction, which excludes from the volume fiber segments disbonded from the matrix, is demonstrated. This analysis is used to estimate the effect of fiber volume on α 1 of T300/934 Gr/Ep during thermal fatigue