Improved models of viscosity and relaxation modulus for epoxy resin during cure

In this work, epoxy resin viscosity was calculated by using reference viscosity and "viscosity-cure" shift factor which was established to research the dependence of viscosity on curing degree. The predicted results were compared with experimental data and the agreements between them were better than those in reference. Generalized Maxwell model was used to characterize the viscoelastic behavior of epoxy resin and the relaxation modulus was modeled by Prony series. A simple model of stress relaxation times was derived as functions of viscosity and stiffness. The stress relaxation times at different curing degrees were calculated after acquiring the stress relaxation times at the reference curing degree. The relaxation modulus predicted by this method agreed well with experimental data. The above results showed that these models could well be used to predict the viscosity and relaxation modulus of thermosetting resin during cure.