ABSTRACT
The time-dependent response of materials can be classified as elastic, viscous, and viscoelastic. On application of a sudden load, which is then held constant, an elastic material undergoes instantaneous deformation. A viscoelastic material combines the behavior of the elastic and viscous material in one, but the response is more complex than just adding the viscous strain to the elastic strain. Most materials are viscoelastic if observed for sufficiently long periods of time, or at a sufficiently high temperature. In other words, most real materials are viscoelastic. All models described so far represent linear viscoelastic materials. In the context of viscoelasticity, linear means that the parameters in the model are not a function of stress. By the correspondence principle, all equations of micromechanics for elastic materials are valid in the Carson domain for linear viscoelastic materials. Most commercial codes have implemented viscoelasticity for isotropic materials.
