Mechanical models standard linear solid

The models mentioned above are based on phenomenologieal quahty and are able to describe either relaxation or ereeping. To describe both effeets the models can be combined to the standard linear solid (SLS) model as shown in Fig. 10a. Consequently, the mechanical impedance of the SLS model Zsls results fi om serial and parallel connection of the single elements and is given by... 

The Maxwell and Voigt models are therefore inadequate to describe the dynamic mechanical behaviour of a polymer, as they do not provide an adequate representation of both the creep and stress relaxation behaviour. A good measure of qualitative improvement could be gained, as in the previous discussion of creep and stress relaxation, by using a three-parameter model, e.g. the standard linear solid, and it is an interesting exercise to show that this model gives a more realistic variation in Gi, G2, and tan 5 with frequency. 

Fig. 5.7 Mechanical models used to represent the viscoelastic behaviour of polymers, (a) Maxwell model, (b) Voigt model, (c) Standard linear solid.

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