Correlation of material lifetime predictions by artificial aging vs. the relaxation master curve

Bahners, Thomas; Schmidt, Markus; Gutmann, Jochen S.

doi:10.1007/s00289-013-0951-y

Cited by 5 publications

(12 citation statements)

References 13 publications

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“…The most frequently used is the time–temperature superposition principle (TTSP) or its modified derivative, [ 5,25 ] for which various approaches have been reported, which enable the calculation of the specific shift factor. [ 26,27 ] Although TTSP is highly effective for amorphous and certain semi‐crystalline polymers, [ 28 ] it fails to adequately describe crystalline or blended polymers. [ 18,19,23 ] Conversely, comprehensive reviews, based on Ferry's [ 20 ] three main rules for validating the TTSP of pure and blended polymers, by Gurp and Palmen [ 18 ] and Boyd, [ 29 ] provide an overview of the differences in the relaxation behavior of polymers having different degrees of crystallinity.…”

Section: Introductionmentioning

confidence: 99%

“…[ 25,27,31,32 ] When the temperature range is too narrow to obtain sufficient data from measurements at various temperatures, the use of a modified time‐superposition principle is recommended to describe the long‐term relaxation or creep behavior. Examples include the time–stress superposition principle (TSSP), [ 28,33–37 ] the time–strain rate superposition principle [ 31,38 ] as well as several other modifications of the superposition principle. [ 18 ] However, each modification has its own limitation.…”

Section: Introductionmentioning

confidence: 99%

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Improved Maxwell Model Approach and its Applicability toward Lifetime Prediction of Biobased Viscoelastic Fibers

Schippers

Bahners

Gutmann

et al. 2021

Macro Materials & Eng

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The evaluation of relaxation measurements is a well‐established technique for predicting the lifetime of polymer materials, with research primarily focusing on increasing prediction accuracy and minimizing material testing time. The current study presents a novel approach toward describing the long‐term behavior of viscoelastic polymers based on the Maxwell model. It assumes a mean relaxation time of the polymer chains in conjunction with a dimensionless number that accounts for averaged polymer chain inhomogeneities. This coefficient is analogous to the dimensionless number, which successfully describes the asymmetry of both the Weibull distribution and of particle size distribution according to the Rosin, Rammler, Sperling and Bennet model. In comparison to earlier models based on time‐superposition principles, the current approach enables lifetime prediction using a single short‐term measurement, which must be taken at a properly chosen applied strain. The applicability of the new model in predicting the long‐term behavior has been demonstrated by the analysis of the relaxation behavior of semi‐crystalline bio‐based fibers.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Improved Maxwell Model Approach and its Applicability toward Lifetime Prediction of Biobased Viscoelastic Fibers

Schippers

Bahners

Gutmann

et al. 2021

Macro Materials & Eng

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“…Extrapolations for lifetime predictions are mainly based on the time–temperature shift (TTS) [22] or/and the Arrhenius approach [23] as mentioned in the ISO 11346 standard [24] for the estimation of rubber lifetime. Recently, lifetime predictions were performed with the combination of mathematical algorithms and short-time mechanical tests [25,26]. However, the presence of DLO effects slows the ageing rate and can distort the data for the lifetime prediction analysis.…”

Section: Introductionmentioning

confidence: 99%

Scission, Cross-Linking, and Physical Relaxation during Thermal Degradation of Elastomers

et al. 2019

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Elastomers are susceptible to chemical ageing, i.e., scission and cross-linking, at high temperatures. This thermally driven ageing process affects their mechanical properties and leads to limited operating time. Continuous and intermittent stress relaxation measurements were conducted on ethylene propylene diene rubber (EPDM) and hydrogenated nitrile butadiene rubber (HNBR) samples for different ageing times and an ageing temperature of 125 °C. The contributions of chain scission and cross-linking were analysed for both materials at different ageing states, elucidating the respective ageing mechanisms. Furthermore, compression set experiments were performed under various test conditions. Adopting the two-network model, compression set values were calculated and compared to the measured data. The additional effect of physical processes to scission and cross-linking during a long-term thermal exposure is quantified through the compression set analysis. The characteristic times relative to the degradation processes are also determined.

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“…In 2013, Bahners et al [2] demonstrated how to evaluate the data of short-term relaxation measurements for a semicrystalline poly(ethylene terephthalate) (PET) fibre according to the Schulz model. Since the modulus E of a fibre, with constant elongation ", follows a symmetrical s-shaped curve if plotted against the logarithm of time [12], the normalized relaxation function (t) can be described by the integral over the Gauss normal distribution as shown in equation 2.…”

Section: Schulz Model For Materials Lifetime Predictionmentioning

confidence: 99%

Revisiting Relaxation Model towards Prediction of Longterm Mechanical Behavior of Semicrystalline Fibers?

Schippers¹,

Bahners²,

Gutmann³

et al. 2021

Preprint

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<p>Tensile testing is a well-established method to assess the maximum strength of a material, while relaxation tests are used to evaluate the viscoelastic behaviour of a polymer. Because of slow viscoelastic changes, significant measurement times are required for reliable descriptions. Therefore the relaxation tests are usually combined with lifetime prediction models to reduce the experimental load. Various traditional models use the time-temperature superposition principle while modificated relaxation models are e.g. based on the time-strain superposition principle (TSSP). Both variations require several measurement series to set up a relaxation master curve (RMC). The basic assumption is that a higher strain corresponds to a higher temperature and a longer load duration, respectively. The paper describes a new model approach which allows to predict the longterm behaviour by using a reduced number of measurements as compared to widely models. The new model is based on the well-known Maxwell model and assumes a mean relaxation time in combination with a relaxation coecient. These parameters account for the inhomogeneity of the individual polymer chains. A dimensionless number, similar to the relaxation coecient, has been successfully introduced for the Weibull distribution and the particle size distribution. The new model allows to derive master curve from one measurement series at a single strain by fitting the data to the model equation.<br></p>

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Correlation of material lifetime predictions by artificial aging vs. the relaxation master curve

Cited by 5 publications

References 13 publications

Improved Maxwell Model Approach and its Applicability toward Lifetime Prediction of Biobased Viscoelastic Fibers

Improved Maxwell Model Approach and its Applicability toward Lifetime Prediction of Biobased Viscoelastic Fibers

Scission, Cross-Linking, and Physical Relaxation during Thermal Degradation of Elastomers

Revisiting Relaxation Model towards Prediction of Longterm Mechanical Behavior of Semicrystalline Fibers?

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