Temperature Variability of Poisson’s Ratio and Its Influence on the Complex Modulus Determined by Dynamic Mechanical Analysis

Carneiro, Vitor Coutinho; Puga, Hélder

doi:10.3390/technologies6030081

Cited by 8 publications

(6 citation statements)

References 20 publications

(23 reference statements)

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“…An experimental data point from Littell et al[36] at 80 °C is also included (open diamond). The predicted Poisson's ratio increases with increasing temperatures, in agreement with experiment[42][43][44][45][46][47], because of increased molecular motion. The predicted Poisson's ratio generally decreases with increasing degrees of cure, as observed experimentally[48,49].…”

supporting

confidence: 85%

Simple and Convenient Correction of Molecular Dynamics Mechanical Property Predictions for Strain Rate, Temperature, and Degree of Cure

Patil

Krieg

Odegard

et al. 2022

Preprint

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It is well-known that all-atom molecular dynamics (MD) predictions of mechanical properties of thermoset resins suffer from multiple accuracy issues associated with their viscous nature. The nanosecond simulation times of MD simulations do not allow for the direct simulation of the molecular conformational relaxations that occur under laboratory time scales. This adversely affects the prediction of mechanical properties at realistic strain rates, intermediate degrees of cure, and elevated temperatures. An efficient method of correcting such MD predictions of elastic properties is proposed and demonstrated. The phenomenological approach is used to correct the predictions of Young’s modulus and Poisson’s ratio for a DGEBF/DETDA epoxy system for intermediate degrees of cure and temperatures above and below the glass transition temperature. The approach uses characterization data from dynamical mechanical analysis temperature sweep experiments. The mathematical formulation and experimental characterization of the correction is described, and the resulting corrections to the predicted elastic properties for various degrees of cure and temperatures are compared with experiment. This correction is particularly important to mitigate the strain-rate effect associated with MD predictions, as well as to accurately correct predicted mechanical properties at elevated temperatures and intermediate degrees of cure to facilitate accurate and efficient composite material process modeling.

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“…The Poisson's ratio also depends on the water content [26]. It should be also used for determining the different elastic moduli for rock engineering design -see Davarpanah et al [27].…”

Section: Discussionmentioning

confidence: 99%

Theoretical Relationship between the Confining Pressure and Poisson’s Ratio of Intact Rock

Lógó

Vásárhelyi²

2022

Period. Polytech. Civil Eng.

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The Poisson’s ratio of the intact rock material is one of the basic material constants for rock engineering calculations in and on rock environments. Recently, several relationships were developed to calculate of the Poisson’s ratio of the intact rock from different mechanical parameters (e.g., rigidity index, cohesion, internal friction angle). This value can be measured under standardized laboratory conditions using traditional uniaxial compressive test at zero confining pressure. Analyzing the laboratory tests carried out at different confining pressure, it was found that this material constant should be increasing as a function of confining pressure. This paper aims to present a theoretical relationship between Poisson’s ratio of intact rock and the confining pressure, using the Hoek-Brown failure criteria. It was assumed that the Poisson’s ratio is increasing linearly, and at the brittle-ductile transaction point, it is 0.5. The proposed relationship can be extended to rock mass, using the Geological Strength Index (GSI).

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“…When a substance is compressed in one direction, Poisson's ratio generally tends to enlarge in the other two directions perpendicular to the direction of compression. This event is called the Poisson's effect in the literature and Poisson's ratio (σ) is stated as a measure of the Poisson's effect (Wang, 2012;Carneiro and Puga, 2018).…”

Section: Methodsmentioning

confidence: 99%

Kılıfsız Optik Fiberlerde Bağıl Direnç Değişimi, Gage Faktörü ve Poisson Oranı’nın Basınç Bağımlılıkları

Günday

2022

KONJES

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Bu makalede, kılıfsız optik fiber çekirdeğine ait bağıl direnç değişimi, gage faktörü ve Poisson oranının basınç bağımlılıkları prensibine dayalı bir dağınık algılama metodu önerilmiştir. Bu metot kullanılarak, basınç bilgilerinin yanı sıra, basınç ile kılıfsız optik fiber çekirdeğinin bağıl direnç değişimi, gage faktörü ve Poisson oranı arasındaki ilişki incelenmiş ve ardından bu parametrelerin sıcaklık bağımlılıkları matematiksel olarak analiz edilmiş ve ayrıca ilgili benzetimler Matlab R2021b ve Simulink ortamında gerçekleştirilmiştir. Buna ek olarak, bu parametreler ve bu parametrelerin sıcaklık bağımlılıkları arasındaki ilişkileri ifade eden birinci dereceden denklemler, eğri uydurma metodundan yararlanılarak türetilmiştir. Basıncın 2.2 × 107 Pa – 12 × 107 Pa aralığındaki değişimi için fiber çekirdeğine ait bağıl direnç değişimleri 0.41 × 10-3 – 2.13 × 10-3 aralığında elde edilmiştir. Diğer bir ifadeyle, fiber çekirdeğinin bağıl direnç değişiminin basınç bağımlılığı 1.841 × 10-2 Rrc(GPa)-1 olarak ifade edilebilmektedir, yani fiber çekirdeği boyunca meydana gelen 1 GPa değerinde basınç değişimi, Rrc değerinde yaklaşık olarak 0.01841 birimlik değişime neden olmaktadır. Ayrıca, gage faktörünün ve Poisson oranının basınç bağımlılıkları, sırasıyla 2.924 × 10-2 GF(GPa)-1 ve 1.462 × 10-2 σ(GPa)-1 olarak elde edilmiştir.

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“…There are still challenges in the characterization of the dynamic mechanical behavior of compliant samples. Even though there are experimental techniques that allow the estimation of the viscoelastic properties of these materials, such as Dynamic Mechanical Analysis, they usually require the pre-tension of the samples [6] and are limited in their range of frequencies (generally up to 200 Hz) [7]. Thus, these methods do not allow the characterization of samples in free-vibration and a wide range of frequencies.…”

Section: Introductionmentioning

confidence: 99%

“…For a cantilever with a rectangular cross-section with a thickness H, Equation (1) may be reorganized into Equation 5, allowing the estimation of the Young's modulus (E) of the material in conformity with the E756-05 standard [26]. C n is the dimensionless constant, related to the eigenmode n associated with the term β n l in Equation (6).…”

mentioning

confidence: 99%

Characterizing the Frequency Response of Compliant Materials by Laser Döppler Vibrometry Coupled Acoustic Excitation

Ricarte¹,

Alves²,

Inácio³

2021

Vibration

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Low-stiffness or compliant materials are inherently difficult to characterize in terms of dynamic mechanical properties. Their free-vibration behavior is not frequently analyzed, given that performing classic vibration testing in these type of materials may imply the tampering of the results by external sources, either by changes in the geometry of the sample, by gravity-induced buckling, or the instrumentation itself (e.g., the mass of accelerometers). This study proposes an approach to determine the frequency response of these types of materials, using a noncontact methodology based on acoustic excitation and displacement measurement by Laser Döppler Vibrometry. The detailed method may be optimized by changing the sample design into a half-cane configuration to increase sample stiffness. This approach significantly increases the sample eigenmodes, facilitating their excitation by the acoustic pressure source. Numerical analysis using the values of the dynamic Young’s modulus from the experimental approaches validates the overall procedure. It is shown that the combination of numerical analysis and the proposed experimental method is a possible route for the determination of the dynamic Young’s modulus of these types of materials by inverse engineering.

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Temperature Variability of Poisson’s Ratio and Its Influence on the Complex Modulus Determined by Dynamic Mechanical Analysis

Cited by 8 publications

References 20 publications

Simple and Convenient Correction of Molecular Dynamics Mechanical Property Predictions for Strain Rate, Temperature, and Degree of Cure

Theoretical Relationship between the Confining Pressure and Poisson’s Ratio of Intact Rock

Kılıfsız Optik Fiberlerde Bağıl Direnç Değişimi, Gage Faktörü ve Poisson Oranı’nın Basınç Bağımlılıkları

Characterizing the Frequency Response of Compliant Materials by Laser Döppler Vibrometry Coupled Acoustic Excitation

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