Modelling of the three-dimensional creep behavior of non-reinforced thermoplastics

In this work a deformation model is discussed for the description of multi-axial creep of non-reinforced polymers. This model is based on the invariant theory and contains three invariants of the stress tensor. The determination of the material constants is investigated through experiments which can be realized in the most simple way. plicability of this model is demonstrated by example of the viscoelastic Poisson’s ratio. tential of the model is a combination of two known potentials for two domains depending on the sign of the first stress invariant. The transition is C0 or C1 continuous. The material behavior during compression stress is seen as incompressible.