Time-dependent behaviour and viscoelastic constitutive modelling of an epoxy polymer

The time-dependent behaviour of a cold cure epoxy polymer was investigated by different types of tests including compression, tension, biaxial loading, strain recovery, stress relaxation, creep and cyclic creep. This epoxy showed nonlinear viscoelastic behaviour since strains were fully recovered after stresses were removed and sufficient time was allowed for the recovery. A linear viscoelastic constitutive model has been extended to the nonlinear regime, and used to simulate the test results. It was found that the model is capable of predicting the observed trends for different types of tests. With one set of specified material constants, the model provides a fairly good prediction for several types of tests. However, this trend may not hold for other types of tests, for which the material constants were not calibrated, although the general trend would be predicted satisfactorily.