Mechanics of a rate-dependent polymer network

Abstract

Pure rubber-like materials usually have little or no rate-dependency during finite straining. In contrast, polymeric materials can exhibit rate-dependent rubber-like responses in the large-strain range. A thermodynamic analysis points to the existence of rate-effects for an elastic network. The presence of reversible crystallization with a rate-dependent feature changes the conformation mobility of the network structure and, subsequently, contributes to the alterations in its elasticity. The internal energy of an elastic polymer network, however, exhibits a step-wise dependence on the applied strain-rates; it alters only at discrete values of strain-rates, every pair of which differs with a unique value that can be described as a sensitivity parameter. At loading rates lower than this parameter, the rate-effects of the polymeric network are absent.

Acknowledgements

The work described in this paper was supported through the Max Planck Forschungspreis in the Engineering Sciences awarded by the Max Planck Gesellschaft, Germany and through a Discovery Grant of the Natural Sciences and Engineering Research Council of Canada, awarded to the second author. The first author would like to thank Stanford University for the continued support on this subject.