Rheological constitutive equations for glassy polymers, based on trap phenomenology

Spathis, G.; Kontou, E.

doi:10.1007/s11043-018-09407-8

Cited by 6 publications

(7 citation statements)

References 21 publications

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“…A viscoelastic model, proposed earlier, [ 20,21 ] was capable of analyzing successfully the thermoelastic‐viscoelastic response of polymeric materials. In a series of works, [ 21,23‐25 ] this theory was proved to describe the main aspects of the nonlinear viscoelastic/viscoplastic response of polymeric systems, namely under monotonic loading, stress relaxation, and creep. Later on, the basic principles of this model were implemented to predict viscoelastic functions from the frequency to the time domain.…”

Section: Constitutive Analysismentioning

confidence: 99%

“…In the second treatment, the distribution function p(u) (designated now as P(u)) can be derived by the loss modulus data. It was shown in Reference [23] that making some approximations in the expression of the loss modulus (Equation (4b), the distribution function, P(u) may be given by:

normalP ((), u) ≅ \frac{2}{μπ} ([], E^{″} ((), \ln ω))

where u=ln(γ/ω). Therefore, the distribution function P(u) can be derived by the experimental values of the loss modulus E″ versus frequency.…”

Section: Constitutive Analysismentioning

confidence: 99%

“…In addition, the determination of parameter γ is crucial, given that it determines the position of the distribution function P(u) along the horizontal axis. According to our previous work, [ 23 ] it was chosen such a value of γ that leads the maximum value of P(u) to be situated at zero position in the horizontal axis. As soon as the distribution function type (p(u) or P(u)) is determined by the two different approaches, the simulation procedure is the same.Following Equations (4a) and (4b) the storage and loss modulus could be calculated, and parameters μ, μ 0, γ, and Σ for the first procedure and μ, μ 0, γ for the second procedure, were evaluated for the best fitting of the experimental data.Regarding elastic stiffness μ, it can be approximated from the high frequency value of the storage modulus.…”

Section: Constitutive Analysismentioning

confidence: 99%

“…The constitutive equation of this analysis was solved for dynamic mechanical, stress‐relaxation, and creep experiments, and the proposed treatment was proved to quite successfully interconvert viscoelastic functions of various polymeric materials. Following the same theory, in a recent work, [ 23 ] it was proposed that the experimental data of the loss modulus can be the basis for the evaluation of the distribution function of the energy barriers.…”

Section: Introductionmentioning

confidence: 99%

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The effectiveness of interconversion methods based on the distributed nature of polymeric structure

Katsourinis

Kontou

2021

Polymer Engineering & Sci

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In the present work, a comparative study on the capability of two approaches to successfully interconvert linear viscoelastic functions is performed. The main concept arises from our previous works, where a polymeric material is treated as a collection of meso‐regions, each one of them with a specific energy barrier. The linking between meso‐regions and their rearrangements leads to a time‐dependent constitutive equation. A crucial issue is the distribution of the energy barriers of the meso‐regions, revealing the importance of the distributed nature of the polymeric structure. In this work, the effect of the distribution type was examined by assuming either a Gaussian distribution function or a normalized loss modulus distribution, which can be evaluated from the loss modulus experimental data. Four different polymers were examined and it was proved that both treatments can satisfactorily predict the creep and relaxation function, once the model parameters are evaluated on the basis of dynamic moduli experimental data.

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Section: Constitutive Analysismentioning

confidence: 99%

normalP ((), u) ≅ \frac{2}{μπ} ([], E^{″} ((), \ln ω))

where u=ln(γ/ω). Therefore, the distribution function P(u) can be derived by the experimental values of the loss modulus E″ versus frequency.…”

Section: Constitutive Analysismentioning

confidence: 99%

Section: Constitutive Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

The effectiveness of interconversion methods based on the distributed nature of polymeric structure

Katsourinis

Kontou

2021

Polymer Engineering & Sci

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“…In ref. [13], the energy barrier distribution function was derived by the loss modulus experimental data. Hereafter, the storage modulus as well as the creep compliance and relaxation modulus could be predicted with the aid of Fourier integrals at a good approximation.…”

Section: Introductionmentioning

confidence: 99%

Model Simulation of Creep and Thermal Ratcheting of Engineering Polymers

Spathis

Kontou

2021

Macro Theory & Simulations

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In the present work, the creep response at specific temperatures and stress level of several polymers has been modeled by a viscoelastic model, analyzed in previous works. In particular, the experimental creep results under thermal cycling of polymers used in bolted flange connections, utilized as components of pressure vessel and piping are employed. The analysis is focused on the experimental results for polymeric flange materials like high density polyethylene and three types of gasket materials, namely poly-tetrafluoroethylene PTFE (expanded e-and virgin v-) and clickable nucleic acid. It has been proved that by the implementation of the model on a simple creep curve at a specific temperature, the model parameters could be evaluated. Hereafter, by imposing a thermal cycling process, two more parameters, associated with thermal ratcheting, could be acquired. It is found that the thermal ratcheting behavior exhibited by the employed materials, could be captured with a good accuracy. Given that the effect of thermal ratcheting on the long-time performance of polymers in targeted applications is a crucial issue, the research findings in the present work are encouraging for the design of appropriate materials, and the prediction of thermal ratcheting.

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Prediction of the non-isothermal creep strain of a glassy polymer on the basis of dynamic analysis results

Kontou

Spathis

2019

Acta Mech

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Rheological constitutive equations for glassy polymers, based on trap phenomenology

Cited by 6 publications

References 21 publications

The effectiveness of interconversion methods based on the distributed nature of polymeric structure

The effectiveness of interconversion methods based on the distributed nature of polymeric structure

Model Simulation of Creep and Thermal Ratcheting of Engineering Polymers

Prediction of the non-isothermal creep strain of a glassy polymer on the basis of dynamic analysis results

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