Chapter 2 Time-temperature-age superposition principle and its application to linear viscoelastic materials

Viscoelastic response such as creep and relaxation are strongly affected by temperature and age for all materials in the range of time when they exhibit viscoelastic effects. Effective time-temperature superposition (ETTSP) is introduced in this chapter to predict long term viscoelastic behavior from short term experimental data. Since the material responds to both temperature and age in the time span of interest, both phenomena are studied, isolated, and described. First, the traditional time-temperature superposition (TTSP) is described and the need to use momentary curves to construct the momentary master curve is addressed. Next, the time-age superposition is described and modeled. Then, the concept of effective time brings everything together into a useful predicting tool. Finally, the methodology is applied to the problem of temperature compensation during long term testing.