Tensile response of graphite/epoxy composites at low temperatures

In this study, the tensile properties of a T700/epoxy composite, which had been cycled with thermo-mechanical loads at low temperatures, were measured using an environmental test chamber. Thermo-mechanical tensile cyclic loading (up to 10 cycles) was applied to T700/epoxy unidirectional laminates at room temperature (RT) to −50 °C, RT to −100 °C, and RT to −150 °C (CT), respectively. Results showed that tensile stiffness significantly increased as temperature decreased, while the thermo-mechanical cycling had little influence on it. Tensile strength, however, decreased as temperature decreased down to CT, while the decreasing rate of strength was reduced after CT cycling. For the analysis of the test results, the coefficients of thermal expansion (CTEs) of the laminate composite specimen, both at RT and CT, were measured, and the interface between fiber and matrix was observed using SEM images.