On the linear viscoelastic limit of polymers—exemplified on poly(methyl methacrylate)

The linear viscoelastic limit of poly(methyl methacrylate) (PMMA) is established on the basis of the Reiner-Weissenberg criterion of strength. The obtained limit is not simply a “strainlimit” or a “stress-limit” but a function of both strain and stress, an energetical limit. In stress-strain representation the limit is independent of time and temperature, which means that the linear or non-linear behavior of the material depends only on the actual values of strain and stress. Some experimental data obtained on PMMA confirm the theory.