Volume changes during stress relaxation in polyethylene

Delin, Mats; Rychwalski, Rodney; Kubát, Michael J.; Kubát, J.

doi:10.1007/bf00398438

Cited by 17 publications

(5 citation statements)

References 32 publications

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“…Several studies present time-dependent Poisson's ratio data. However, the data are limited to low temperature [2][3][4][5][6], large strains [7][8][9], or the experimental technique is applicable to only certain materials [10]. An early work by [11] presents only instantaneous values for the Poisson's ratio of polymers at large strains.…”

Section: Introductionmentioning

confidence: 99%

Cure-dependent Viscoelastic Poisson’s Ratio of Epoxy

2007

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The evolution of the lateral contraction ratio of two commercial (high and low temperature cure) epoxy resins is studied in uniaxial tension using moiré interferometry. The ratio of transverse to axial strains evolves from an elastic value of about 0.40 to a rubbery plateau value of 0.49 at long times. Furthermore, the data indicate that the contraction ratio follows timetemperature superposition with a shift function indistinguishable from other axial viscoelastic functions. The lateral contraction behavior at several cure states past gelation was measured and a model is proposed to describe the cure dependence.

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Section: Introductionmentioning

confidence: 99%

Cure-dependent Viscoelastic Poisson’s Ratio of Epoxy

2007

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“…In both cases its viscoelastic nature is completely neglected [1]. Nevertheless, it was shown that only in few cases the assumption of a constant Poisson's ratio can be reasonably considered valid [2,4], and that neglecting its time and temperature dependence may lead to predicting models markedly deviating from the experimental observations [5][6][7]. More detailed information on the viscoelastic behaviour of Poisson's ratio is therefore important not only in principle [8][9][10], but also for practical reasons.…”

Section: Introductionmentioning

confidence: 99%

Time and temperature effects on Poisson’s ratio of poly(butylene terephthalate)

Pandini¹,

Pegoretti²

2011

Express Polym. Lett.

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Abstract. The viscoelastic nature of the Poisson's ratio of a semicrystalline poly (butylene terephthalate) is highlighted by investigating its dependence on time, temperature and strain rate, under two types of loading conditions: i) constant deformation rate tests, in which the transverse strain is measured in tensile ramps at various temperatures and at two strain rates; and ii) constant deformation tests, in which, under a constant axial deformation, the transverse strain is measured as a function of time in isothermal experiments performed at various temperatures. In both testing configurations, axial and transverse deformations are measured by means of a biaxial contact extensometer, and a correction procedure is adopted in order to compensate the lateral penetration of the extensometer knives. Poisson's ratio displays the typical features of a retardation function, increasing with time and temperature, and decreasing with strain rate. This behaviour has been compared to that of simultaneously measured relaxation modulus.

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“…Although small variation of stress relaxation time between solid material and foams was found, no statistically significant difference could be extracted for porous materials. It is noted that the individual relaxation processes can be thought of as in-dependent, referring, for example, to the paper [26].…”

Section: Stress Relaxation Analysismentioning

confidence: 99%

“…The three methods showed good agreement at different values of porosity. It was concluded that It is noted that the individual relaxation processes can be thought of as in-dependent, referring, for example, to the paper [26].…”

Section: Stress Relaxation Analysismentioning

confidence: 99%

Analysis of Stress Relaxation in Bulk and Porous Ultra-High Molecular Weight Polyethylene (UHMWPE)

et al. 2022

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The reported study was devoted to the investigation of viscoelastic behavior for solid and porous ultra-high molecular weight polyethylene (UHMWPE) under compression. The obtained experimental stress curves were interpreted using a two-term Prony series to represent the superposition of two coexisting activation processes corresponding to long molecular (~160 s) and short structural (~20 s) time scales, respectively, leading to good statistical correlation with the observations. In the case of porous polymer, the internal strain redistribution during relaxation was quantified using digital image correlation (DIC) analysis. The strongly inhomogeneous deformation of the porous polymer was found not to affect the relaxation times. To illustrate the possibility of generalizing the results to three dimensions, X-ray tomography was used to examine the porous structure relaxation at the macro- and micro-scale levels. DIC analysis revealed positive correlation between the applied force and relative density. The apparent stiffness variation for UHMWPE foams with mixed open and closed cells was described using a newly proposed three-term expression. Furthermore, in situ tensile loading and X-ray scattering study was applied for isotropic solid UHMWPE specimens to investigate the evolution of internal structure and orientation during drawing and stress relaxation in another loading mode.

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Volume changes during stress relaxation in polyethylene

Cited by 17 publications

References 32 publications

Cure-dependent Viscoelastic Poisson’s Ratio of Epoxy

Cure-dependent Viscoelastic Poisson’s Ratio of Epoxy

Time and temperature effects on Poisson’s ratio of poly(butylene terephthalate)

Analysis of Stress Relaxation in Bulk and Porous Ultra-High Molecular Weight Polyethylene (UHMWPE)

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