Yielding behavior of model epoxy matrices for fiber reinforced composites: Effect of strain rate and temperature

The yield behaviors of cured epoxy resins, prepared from the two major monomers used in commercial high performance matrices for polymer fiber composites, were investigated as a function of temperature and strain rate. Tetraglycidyldiaminodiphenylmethane TGDDM (Araldite MY721) and Triglycidyl p -aminophenol TGAP (Araldite MY0510) have been cured with 4-4' Diaminodiphenylsulphone (DDS) hardener. The test specimens were subjected to uniaxial compressive deformation over a range of temperature and strain rate. In both systems, the compressive yield strength and modulus increased linearly as the strain rate increased. An inverse trend was observed at high temperatures. A master curve was obtained from the strain rate-temperature superposition of the compressive yield strength data. The temperature dependence of the shift factors led to the evaluation of an Arrhenius type activation energy. Trifunctional MY0510 exhibited a higher activation energy than did Tetrafunctional MY721.