The Effect of Time and Temperature on the Flexural Strength of a Silica Particle Filled Epoxy Resin

Composite materials that use an epoxy as a matrix resins have superior mechanical properties but these materials exhibit time and temperature behavior when used for long periods and under high temperatures. This time and temperature behavior has not been fully explained. The purpose of this paper is to further describe this time and temperature behavior, therefore increasing the reliability of these types of composite materials. The time and temperature dependence of flexural strength was examined by flexural static and fatigue testing. Initially the neat resin's viscoelastic mechanical behavior was determined experimentally to be later compared to the composites. Static tests were carried out at various constant deflection rates and temperatures below the glass transition temperature of the epoxy resin. It was shown that the time-temperature superposition principle is applicable for the flexural static strength. Comparison of the neat resin and the composite results show that the neat resin is a major influence on the time and temperature behavior of the composite materials static strength behavior. Fatigue tests were carried out at several stress ratios and various temperatures below the glass transition temperature of the matrix resin. It was shown that the time-temperature superposition principle is applicable for the initial flexural fatigue strength by using the time-temperature behavior of the matrix resin. As temperature and stress ratio increased, the creep influence increased in both the flexural strength and the modulus.