The effect of time and temperature on flexural creep and fatigue strength of a silica particle filled epoxy resin

Composite materials that use an epoxy resin as a matrix resins have superio r mechanical properties over standard structural materials, but these mater ials exhibit time and temperature behavior when used for long periods and u nder high temperatures. This time and temperature behavior has not been ful ly explained. The purpose of this paper is to further describe this time an d temperature behavior, increasing the reliability of this class of composi te materials. The time and temperature dependence of flexural strength was examined by creep and fatigue testing. Flexural creep tests were carried ou t at various temperatures below the glass transition temperature. Flexural fatigue tests were carried out at various stress ratios, temperatures below the glass transition temperature and 2 frequencies. The time-temperature s uperposition principle held for the flexural creep strength of this materia l. A method to predict flexural creep strength based on the static strength master curve and the cumulative damage law is proposed. When the fatigue f requency was decreased while temperature and stress ratio are held constant the flexural fatigue strength decreases. The time-temperature superpositio n principle was also found to hold for the flexural fatigue strength with r espect to frequency. (C) 1999 Kluwer Academic Publishers.