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Relaxation during stress‐strain cycles of networks in the glass transition range and its description with an onsager approach
Author(s) -
Kraus Volker,
Kilian HannsGeorg
Publication year - 1993
Publication title -
makromolekulare chemie. macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 0258-0322
DOI - 10.1002/masy.19930760116
Subject(s) - relaxation (psychology) , isothermal process , glass transition , thermodynamics , strain rate , stress relaxation , stress (linguistics) , non equilibrium thermodynamics , coupling (piping) , strain (injury) , materials science , mode coupling , van der waals force , function (biology) , condensed matter physics , statistical physics , physics , polymer , creep , quantum mechanics , molecule , medicine , psychology , social psychology , linguistics , philosophy , evolutionary biology , biology , composite material , metallurgy
Temperature and strain rate dependence of large cyclic deformations are investigated. The quasi‐static stress‐strain behaviour is described in terms of the van der Waals theory for polymer networks. Within the framework of irreversible thermodynamics, the Gibbs function is extended by hidden variables which represent a set of orthogonal relaxation modes of the Onsager type. These modes are linearly coupled to the quasi static reference state of the network (relaxation mode coupling model). This results in a time dependent expression for the nominal force, where the mode independent relaxation time spectrum plays a dominant role. For high temperatures or low strain rates, the temperature dependence of the spectrum obeys the WLF equation. Approaching the glass transition region, a limitation of the WLF equation is considered. The transition between isothermal and non isothermal deformation is determined.