Viscoplasticity and large-scale chain relaxation in glassy-polymeric strain hardening

Abstract

A simple theory for glassy polymeric mechanical response which accounts for large scale chain relaxation is presented. It captures the crossover from perfect-plastic response to strong strain hardening as the degree of polymerization $N$ increases, without invoking entanglements. By relating hardening to interactions on the scale of monomers and chain segments, we correctly predict its magnitude. Strain activated relaxation arising from the need to maintain constant chain contour length reduces the $N$ dependence of the characteristic relaxation time by a factor $\sim \dot{\epsilon }N$ during active deformation at strain rate $\dot{\epsilon }$. This prediction is consistent with results from recent experiments and simulations, and we suggest how it may be further tested experimentally.

The theoretical treatment of the mechanical response has been significantly revised, and the arguments for coherent relaxation during active deformation made more transparent

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Cited by in corpus (7)

• Strain-stiffening in random packings of entangled granular chains
• Why is Understanding Glassy Polymer Mechanics So Difficult?
• A Simple Model for the Deformation-Induced Relaxation of Glassy Polymers
• Modeling the Relaxation of Polymer Glasses under Shear and Elongational Loads
• Microscopic Activated Dynamics Theory of the Shear Rheology and Stress Overshoot in Ultra-Dense Glass-Forming Fluids and Colloidal Suspensions
• Relaxation time of a polymer glass stretched at very large strains
• Strain stiffening due to stretching of entangled particles in random packings of granular materials