Viscoelastic Properties of an Epoxy Resin during Cure

The cure dependent relaxation modulus of an epoxy resin was investigated over the entire range of cure extent. Parallel plate rheometry was used to measure the material behavior below the gel point of the epoxy network. Creep testing in three-point bend was used for specimens cured past gelation. All data were converted to the stress relaxation modulus for comparison of the material behavior among the various cure states and between the two experimental techniques. The data were used to develop a practical model for predicting the cure dependence of the relaxation modulus throughout cure under varying processing conditions.