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Viscoelastic-viscoplastic combined constitutive model for glassy amorphous polymers under loading/unloading/no-load states

Seishiro Matsubara (Department of Civil Engineering, Tohoku University, Sendai, Japan)
Kenjiro Terada (International Research Institute of Disaster Science, Tohoku University, Sendai, Japan)
Ryusei Maeda (Mechanical Design and Analysis Corporation, Chofu, Japan)
Takaya Kobayashi (Mechanical Design and Analysis Corporation, Chofu, Japan)
Masanobu Murata (Nagoya Municipal Industrial Research Institute, Nagoya, Japan)
Takuya Sumiyama (Toyobo Co. Ltd., Research Center, Otsu, Japan)
Kenji Furuichi (Toyobo Co. Ltd., Research Center, Otsu, Japan)
Chisato Nonomura (Toyobo Co. Ltd., Research Center, Otsu, Japan)

Engineering Computations

ISSN: 0264-4401

Publication date: 15 February 2020

Abstract

Purpose

This study aims to propose a novel viscoelastic–viscoplastic combined constitutive model for glassy amorphous polymers within the framework of thermodynamics at finite strain that is capable of capturing their rate-dependent inelastic mechanical behavior in wide ranges of deformation rate and amount.

Design/methodology/approach

The rheology model whose viscoelastic and viscoplastic elements are connected in series is set in accordance with the multi-mechanism theory. Then, the constitutive functions are formulated on the basis of the multiplicative decomposition of the deformation gradient implicated by the rheology model within the framework of thermodynamics. Dynamic mechanical analysis (DMA) and loading/unloading/no-load tests for polycarbonate (PC) are conducted to identify the material parameters and demonstrate the capability of the proposed model.

Findings

The performance was validated in comparison with the series of the test results with different rates and amounts of deformation before unloading together. It has been confirmed that the proposed model can accommodate various material behaviors empirically observed, such as rate-dependent elasticity, elastic hysteresis, strain softening, orientation hardening and strain recovery.

Originality/value

This paper presents a novel rheological constitutive model in which the viscoelastic element connected in series with the viscoplastic one exclusively represents the elastic behavior, and each material response is formulated according to the multiplicatively decomposed deformation gradients. In particular, the yield strength followed by the isotropic hardening reflects the relaxation characteristics in the viscoelastic constitutive functions so that the glass transition temperature could be variant within the wide range of deformation rate. Consequently, the model enables us to properly represent the loading process up to large deformation regime followed by unloading and no-load processes.

Keywords

Citation

Matsubara, S., Terada, K., Maeda, R., Kobayashi, T., Murata, M., Sumiyama, T., Furuichi, K. and Nonomura, C. (2020), "Viscoelastic-viscoplastic combined constitutive model for glassy amorphous polymers under loading/unloading/no-load states", Engineering Computations, Vol. 37 No. 5, pp. 1703-1735. https://doi.org/10.1108/EC-05-2019-0197

Publisher

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Emerald Publishing Limited

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