A three-dimensional shear transformation zone theory for glassy polymers
Lin J, Zhao W, Xiao R (2026)
Publication Type: Journal article
Publication year: 2026
Journal
Pages Range: 104628
Article Number: 104628
DOI: 10.1016/j.ijplas.2026.104628
Abstract
Developing constitutive models for the highly nonlinear behaviors of glassy polymers, such as yielding and strain hardening, is important for their engineering applications. Yielding is closely tied to nonequilibrium thermodynamics, often referred to as physical aging, while strain hardening is associated with the oriented microstructures of the polymer network, which further contribute to the Bauschinger effect in pre-deformed glassy polymers. To capture these nonlinear mechanical responses, we have developed a three-dimensional viscoplastic model grounded in shear transformation zone (STZ) theory, linking the plastic flow to the STZ microdynamics. The collective behavior of STZs is characterized by two statistical variables: the density and orientation tensor, both governed by first-order evolution equations. We established a conceptual relationship between these STZ variables and the plastic flow tensor by incorporating a prefactor that combines the amplitude of chain stretching with the angle between the driven stress and STZ orientation. Additionally, an effective temperature model has been integrated to capture nonequilibrium thermodynamics. The model was applied to quantitatively describe the stress responses of glassy polymers in uniaxial deformation and plane strain tests. The simulation results demonstrate that the model quantitatively captures physical aging under various thermal and mechanical conditions, as well as the Bauschinger effect, reflected in distinct stress responses of pre-deformed glassy polymers in opposite loading directions. This work extends the STZ model to the finite deformation three-dimensional condition, bridging the gap between the intricate microscopic mechanisms governing STZ transformation and the complex constitutive behaviors of glassy polymers.
Authors with CRIS profile
Involved external institutions
Zhejiang University / Chekiang University / 浙江大学
China (CN)
Ningbo University of Technology (NingboTech University)
China (CN)
China (CN)
Ningbo University of Technology (NingboTech University)
China (CN)
How to cite
APA:
Lin, J., Zhao, W., & Xiao, R. (2026). A three-dimensional shear transformation zone theory for glassy polymers. International Journal of Plasticity, 104628. https://doi.org/10.1016/j.ijplas.2026.104628
MLA:
Lin, Ji, Wuyang Zhao, and Rui Xiao. "A three-dimensional shear transformation zone theory for glassy polymers." International Journal of Plasticity (2026): 104628.
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