The Nonlinear Viscoelastic Response of Glassy Polymers Subjected to Physical Aging

Abstract

Constitutive equations are developed for the nonlinear viscoelastic behavior of amorphous glassy polymers in the sub-yield region. A polymeric glass is treated as an ensemble of cooperatively rearranging regions bridged by links. Stress-strain relations are derived and verified by comparison with experimental data in static mechanical tests on polycarbonate and poly(methyl methacrylate). We analyze the effects of the straining state (tension, compression and torsion), strain intensity, temperature and time of annealing on stress relaxation. Fair agreement is demonstrated between observations and results of numerical simulation.