Reinforcement and Nonlinear Viscoelasticity of Polymer Melts Containing Mixtures of Nanofillers

2005 ◽  
Vol 78 (2) ◽  
pp. 258-270 ◽  
Author(s):  
S. S. Sternstein ◽  
G. Ramorino ◽  
B. Jiang ◽  
Ai-Jun Zhu
Keyword(s):  
Storage Modulus ◽  
Loss Factor ◽  
Nearest Neighbor ◽  
Viscoelastic Behavior ◽  
Polymer Melt ◽  
Filler Concentration ◽  
Mixture Ratio ◽  
Particle Spacing ◽  
Nonlinear Viscoelastic ◽  
Neighbor Particle

Abstract The reinforcement and concomitant nonlinear viscoelastic behavior have been investigated for several composites of linear polymer melt with various binary mixtures of nanofillers having different surface chemistries and particle sizes. The dependence of storage modulus and loss factor on dynamic shear strain amplitude has been obtained for several compositions of each binary filler pair. Composites with mixed fillers display nonlinear interactions that are filler pair/matrix specific. Total filler concentration appears to be a major factor, suggesting that nearest neighbor particle spacing is crucial even if the neighbors are of a different filler type. The results are consistent with the theory recently proposed by Sternstein and Zhu in which the high reinforcement by nanofillers is due to the trapping of entanglements and the resultant effects on matrix chain mobility and entropic elasticity. At high strain amplitudes, the storage modulus and loss factor of the composites with binary filler mixtures are found to be nearly independent of the filler mixture ratio, and dependent only on the total filler concentration. A “partial molar” storage modulus for mixed filler composites is defined for future considerations, and specific interactions are presented for two binary filler systems.

Nonlinear Viscoelastic Finite Element Analysis of Adhesive Joints

1988 ◽  
Vol 16 (3) ◽  
pp. 146-170 ◽  
Author(s):  
S. Roy ◽  
J. N. Reddy
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Viscoelastic Behavior ◽  
Bonded Joints ◽  
Adhesively Bonded ◽  
Element Analysis ◽  
Adhesively Bonded Joints ◽  
Nonlinear Viscoelastic ◽  
Structural Failures ◽  
Updated Lagrangian

Abstract A good understanding of the process of adhesion from the mechanics viewpoint and the predictive capability for structural failures associated with adhesively bonded joints require a realistic modeling (both constitutive and kinematic) of the constituent materials. The present investigation deals with the development of an Updated Lagrangian formulation and the associated finite element analysis of adhesively bonded joints. The formulation accounts for the geometric nonlinearity of the adherends and the nonlinear viscoelastic behavior of the adhesive. Sample numerical problems are presented to show the stress and strain distributions in bonded joints.

Influence of κ-Carrageenan, Modified Starch and Inulin Addition on Rheological and Sensory Properties of Non-fat and Non-added Sugar Dairy Dessert

2020 ◽  
Vol 16 (4) ◽  
pp. 462-469
Author(s):  
Zhaleh Sheidaei ◽  
Bahareh Sarmadi ◽  
Seyede M. Hosseini ◽  
Fardin Javanmardi ◽  
Kianoush Khosravi-Darani ◽  
...  
Keyword(s):  
Storage Modulus ◽  
Loss Modulus ◽  
Viscoelastic Behavior ◽  
Textural Properties ◽  
Complex Viscosity ◽  
Sensory Properties ◽  
Modified Starch ◽  
Consumer Health ◽  
Added Sugar ◽  
Textural Parameters

<P>Background: The high amounts of fat, sugar and calorie existing in dairy desserts can lead to increase the risk of health problems. Therefore, the development of functional and dietary forms of these products can help the consumer health. </P><P> Objective: This study aims to investigate the effects of &#954;-carrageenan, modified starch and inulin addition on rheological and sensory properties of non-fat and non-added sugar dairy dessert. </P><P> Methods: In order to determine the viscoelastic behavior of samples, oscillatory test was carried out and the values of storage modulus (G′), loss modulus (G″), loss angle tangent (tan &#948;) and complex viscosity (&#951;*) were measured. TPA test was used for analysis of the desserts’ texture and textural parameters of samples containing different concentrations of carrageenan, starch and inulin were calculated. </P><P> Results: All treatments showed a viscoelastic gel structure with the storage modulus higher than the loss modulus values. Increasing amounts of &#954;-carrageenan and modified starch caused an increase in G′ and G″ as well as &#951;* and a decrease in tan &#948;. Also, firmness and cohesiveness were enhanced. The trained panelists gave the highest score to the treatment with 0.1% &#954;-carrageenan, 2.5% starch and 5.5% inulin (sucralose as constant = 0.25%) and this sample was the best treatment with desirable attributes for the production of non-fat and non-added sugar dairy dessert. </P><P> Conclusion: It can be concluded that the concentration of &#954;-carrageenan and starch strongly influenced the rheological and textural properties of dairy desserts, whereas the inulin content had little effect on these attributes.</P>

scholarly journals Adaptive settings for the nearest-neighbor particle tracking algorithm

2014 ◽  
Vol 31 (8) ◽  
pp. 1279-1285 ◽  
Author(s):  
Javier Mazzaferri ◽  
Joannie Roy ◽  
Stephane Lefrancois ◽  
Santiago Costantino
Keyword(s):  
Particle Tracking ◽  
Nearest Neighbor ◽  
Tracking Algorithm ◽  
Neighbor Particle ◽  
Particle Tracking Algorithm

scholarly journals Mechanical Consequences of Dynamically Loaded NiTi Wires under Typical Actuator Conditions in Rehabilitation and Neuroscience

2021 ◽  
Vol 12 (1) ◽  
pp. 4
Author(s):  
Umut D. Çakmak ◽  
Zoltán Major ◽  
Michael Fischlschweiger
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Storage Modulus ◽  
Loss Factor ◽  
Empirical Relation ◽  
Material Behavior ◽  
Chemical Compositions ◽  
Loading Frequency ◽  
Frequency Dependency ◽  
Controlled Conditions

In the field of rehabilitation and neuroscience, shape memory alloys play a crucial role as lightweight actuators. Devices are exploiting the shape memory effect by transforming heat into mechanical work. In rehabilitation applications, dynamic loading of the respective device occurs, which in turn influences the mechanical consequences of the phase transforming alloy. Hence in this work, dynamic thermomechanical material behavior of temperature-triggered phase transforming NiTi shape memory alloy (SMA) wires with different chemical compositions and geometries was experimentally investigated. Storage modulus and mechanical loss factor of NiTi alloys at different temperatures and loading frequencies were analyzed under force-controlled conditions. Counterintuitive storage modulus- and loss factor-dependent trends regarding the loading frequency dependency of the mechanical properties on the materials’ composition and geometry were, hence, obtained. It was revealed that loss factors showed a pronounced loading frequency dependency, whereas the storage modulus was not affected. It was shown that force-controlled conditions led to a lower storage modulus than expected. Furthermore, it turned out that a simple empirical relation could capture the characteristic temperature dependency of the storage modulus, which is an important input relation for modeling the rehabilitation device behavior under different dynamic and temperature loading conditions, taking directly into account the material behavior of the shape memory alloy.

Identification of Nonlinear Viscoelastic Models of Flexible Polyurethane Foam From Uniaxial Compression Data

2016 ◽  
Vol 138 (2) ◽  
Author(s):  
Yousof Azizi ◽  
Patricia Davies ◽  
Anil K. Bajaj
Keyword(s):  
Uniaxial Compression ◽  
Viscoelastic Model ◽  
Viscoelastic Behavior ◽  
Model Parameters ◽  
Viscoelastic Models ◽  
Nonlinear Viscoelastic ◽  
Compression Data ◽  
Computationally Intensive ◽  
Nonlinear Viscoelastic Model ◽  
Flexible Polyurethane

Flexible polyethylene foam is used in many engineering applications. It exhibits nonlinear and viscoelastic behavior which makes it difficult to model. To date, several models have been developed to characterize the complex behavior of foams. These attempts include the computationally intensive microstructural models to continuum models that capture the macroscale behavior of the foam materials. In this research, a nonlinear viscoelastic model, which is an extension to previously developed models, is proposed and its ability to capture foam response in uniaxial compression is investigated. It is hypothesized that total stress can be decomposed into the sum of a nonlinear elastic component, modeled by a higher-order polynomial, and a nonlinear hereditary type viscoelastic component. System identification procedures were developed to estimate the model parameters using uniaxial cyclic compression data from experiments conducted at six different rates. The estimated model parameters for individual tests were used to develop a model with parameters that are a function of strain rates. The parameter estimation technique was modified to also develop a comprehensive model which captures the uniaxial behavior of all six tests. The performance of this model was compared to that of other nonlinear viscoelastic models.

scholarly journals Simultaneous Characterization of Relaxation, Creep, Dissipation, and Hysteresis by Fractional-Order Constitutive Models

2021 ◽  
Vol 5 (2) ◽  
pp. 36
Author(s):  
Jun-Sheng Duan ◽  
Di-Chen Hu ◽  
Yang-Quan Chen
Keyword(s):  
Constitutive Model ◽  
Storage Modulus ◽  
Loss Factor ◽  
Creep Compliance ◽  
Loss Modulus ◽  
Constitutive Models ◽  
Stationary Points ◽  
Logarithmic Scale ◽  
Zener Model ◽  
Fractional Zener Model

We considered relaxation, creep, dissipation, and hysteresis resulting from a six-parameter fractional constitutive model and its particular cases. The storage modulus, loss modulus, and loss factor, as well as their characteristics based on the thermodynamic requirements, were investigated. It was proved that for the fractional Maxwell model, the storage modulus increases monotonically, while the loss modulus has symmetrical peaks for its curve against the logarithmic scale log(ω), and for the fractional Zener model, the storage modulus monotonically increases while the loss modulus and the loss factor have symmetrical peaks for their curves against the logarithmic scale log(ω). The peak values and corresponding stationary points were analytically given. The relaxation modulus and the creep compliance for the six-parameter fractional constitutive model were given in terms of the Mittag–Leffler functions. Finally, the stress–strain hysteresis loops were simulated by making use of the derived creep compliance for the fractional Zener model. These results show that the fractional constitutive models could characterize the relaxation, creep, dissipation, and hysteresis phenomena of viscoelastic bodies, and fractional orders α and β could be used to model real-world physical properties well.

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