Electroelasticity of dielectric elastomers based on molecular chain statistics

2018 ◽  
Vol 24 (3) ◽  
pp. 862-873 ◽  
Author(s):  
Mikhail Itskov ◽  
Vu Ngoc Khiêm ◽  
Sugeng Waluyo
Keyword(s):  
Constitutive Model ◽  
Polymer Chain ◽  
Mechanical Response ◽  
Three Dimensional ◽  
Polymer Chains ◽  
Molecular Chain ◽  
Dielectric Elastomers ◽  
Finite Extensibility ◽  
Single Polymer Chain ◽  
Non Gaussian

The mechanical response of dielectric elastomers can be influenced or even controlled by an imposed electric field. It can, for example, cause mechanical stress or strain without any applied load; this phenomenon is referred to as electrostriction. There are many purely phenomenological hyperelastic models describing this electroactive response of dielectric elastomers. In this contribution, we propose an electromechanical constitutive model based on molecular chain statistics. The model considers polarization of single polymer chain segments and takes into account their directional distribution. The latter results from non-Gaussian chain statistics, taking finite extensibility of polymer chains into account. The resulting (one-dimensional) electric potential of a single polymer chain is further generalized to the (three-dimensional) network potential. To this end, we apply directional averaging on the basis of numerical integration over a unit sphere. In a special case of the eight-direction (Arruda–Boyce) model, directional averaging is obtained analytically. This results in an invariant-based electroelastic constitutive model of dielectric elastomers. The model includes a small number of physically interpretable material constants and demonstrates good agreement with experimental data, with respect to the electroactive response and electrostriction of dielectric elastomers.

scholarly journals A nonlinear strain-rate dependent constitutive model for uncured rubber materials under large deformation

2020 ◽  
Vol 37 ◽  
pp. 118-125
Author(s):  
Weihua Zhou ◽  
Changqing Fang ◽  
Huifeng Tan ◽  
Huiyu Sun
Keyword(s):  
Constitutive Model ◽  
Large Deformation ◽  
Mechanical Response ◽  
Uniaxial Tensile ◽  
Hysteresis Phenomenon ◽  
Mechanical Behaviors ◽  
Nonlinear Constitutive Model ◽  
Rate Dependent ◽  
Parallel Networks ◽  
Non Gaussian

Abstract Uncured rubber possesses remarkable hyperelastic and viscoelastic properties while it undergoes large deformation; therefore, it has wide application prospects and attracts great research interests from academia and industry. In this paper, a nonlinear constitutive model with two parallel networks is developed to describe the mechanical response of uncured rubber. The constitutive model is incorporated with the Eying model to describe the hysteresis phenomenon and viscous flow criterion, and the hyperelastic properties under large deformation are captured by a non-Gaussian chain molecular network model. Based on the model, the mechanical behaviors of hyperelasticity, viscoelasticity and hysteresis under different strain rates are investigated. Furthermore, the constitutive model is employed to estimate uniaxial tensile, cyclic loading–unloading and multistep tensile relaxation mechanical behaviors of uncured rubber, and the prediction results show good agreement with the test data. The nonlinear mechanical constitutive model provides an efficient method for predicting the mechanical response of uncured rubber materials.

A Micromechanically Based Constitutive Model for the Inelastic and Swelling Behaviors in Double Network Hydrogels

2015 ◽  
Vol 83 (2) ◽  
Author(s):  
Yin Liu ◽  
Hongwu Zhang ◽  
Yonggang Zheng
Keyword(s):  
Constitutive Model ◽  
Strain Energy ◽  
Polymer Chains ◽  
Loading Path ◽  
Induced Anisotropy ◽  
Double Network ◽  
Strain Energy Density Function ◽  
Damage Process ◽  
Single Polymer Chain ◽  
Swelling Behaviors

This paper presents a micromechanically based constitutive model within the framework of the continuum mechanics to characterize the inelastic elastomeric and swelling behaviors of double network (DN) hydrogels, such as the stress-softening, necking instability, hardening, and stretch-induced anisotropy. The strain-energy density function of the material is decomposed into two independent contributions from the tight and brittle first network and the soft and loose second network, each of which is obtained by integrating the strain energy of one-dimensional (1D) polymer chains in each direction of a unit sphere. The damage process is derived from the irreversible breakages of sacrificial chains in the first network and characterized by the directional stretch-dependent evolution laws for the equivalent modulus and the locking stretch in the non-Gauss statistical model of a single polymer chain. The constitutive model with the optimized-material evolution law predicts stress–stretch curves in a good agreement with the experimental results during loading, unloading, and reloading paths for both ionic and covalent DN hydrogels. The deformation-induced anisotropy is investigated and demonstrated by the constitutive model for the free swelling of damaged specimen. The constitutive model is embedded into the finite-element (FE) procedure and proved to be efficient to model the necking and neck propagation in the plane-strain uniaxial elongation. Based on the procedure, the effects of imperfection and boundary conditions on the loading path and the material evolution during different stages of deformation are investigated.

scholarly journals Direct observation of morphological transition for an adsorbed single polymer chain

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Yukari Oda ◽  
Daisuke Kawaguchi ◽  
Yuma Morimitsu ◽  
Satoru Yamamoto ◽  
Keiji Tanaka
Keyword(s):  
Polymer Chain ◽  
Synthetic Polymer ◽  
Polymer Chains ◽  
Dynamics Simulation ◽  
Morphological Transition ◽  
Nano Composite ◽  
Force Microscopy ◽  
Local Conformation ◽  
Atomic Force ◽  
Single Polymer Chain

AbstractA better understanding of the structure of polymers at solid interfaces is crucial for designing various polymer nano-composite materials from structural materials to nanomaterials for use in industry. To this end, the first step is to obtain information on how synthetic polymer chains adsorb onto a solid surface. We closely followed the trajectory of a single polymer chain on the surface as a function of temperature using atomic force microscopy. Combining the results with a full-atomistic molecular dynamics simulation revealed that the chain became more rigid on the way to reaching a pseudo-equilibrium state, accompanied by a change in its local conformation from mainly loops to trains. This information will be useful for regulating the physical properties of polymers at the interface.

scholarly journals Experimentally Validated Microstructural 3D Constitutive Model of Coronary Arterial Media

2011 ◽  
Vol 133 (3) ◽  
Author(s):  
Yaniv Hollander ◽  
David Durban ◽  
Xiao Lu ◽  
Ghassan S. Kassab ◽  
Yoram Lanir
Keyword(s):  
Constitutive Model ◽  
Mechanical Response ◽  
Three Dimensional ◽  
Vascular Diseases ◽  
Structural Features ◽  
Stretch Ratio ◽  
Global Media ◽  
Biaxial Tests ◽  
Orientational Distribution ◽  
The Media

Accurate modeling of arterial response to physiological or pathological loads may shed light on the processes leading to initiation and progression of a number of vascular diseases and may serve as a tool for prediction and diagnosis. In this study, a microstructure based hyperelastic constitutive model is developed for passive media of porcine coronary arteries. The most general model contains 12 independent parameters representing the three-dimensional inner fibrous structure of the media and includes the effects of residual stresses and osmotic swelling. Parameter estimation and model validation were based on mechanical data of porcine left anterior descending (LAD) media under radial inflation, axial extension, and twist tests. The results show that a reduced four parameter model is sufficient to reliably predict the passive mechanical properties. These parameters represent the stiffness and the helical orientation of each lamellae fiber and the stiffness of the interlamellar struts interconnecting these lamellae. Other structural features, such as orientational distribution of helical fibers and anisotropy of the interlamellar network, as well as possible transmural distribution of structural features, were found to have little effect on the global media mechanical response. It is shown that the model provides good predictions of the LAD media twist response based on parameters estimated from only biaxial tests of inflation and extension. In addition, good predictive capabilities are demonstrated for the model behavior at high axial stretch ratio based on data of law stretches.

Dynamic Nanofishing of Single Polymer Chains

2009 ◽  
Vol 82 (2) ◽  
pp. 271-282
Author(s):  
Ken Nakajima ◽  
Toshio Nishi
Keyword(s):  
Polymer Chain ◽  
Single Molecule ◽  
Structural Information ◽  
Persistence Length ◽  
Frictional Coefficient ◽  
Polymer Chains ◽  
Contour Length ◽  
Single Polymer Chain ◽  
Afm Cantilever ◽  
Solvent Molecules

Abstract Single molecule force spectroscopy (SMFS) realized by atomic force microscope (AFM) on a single polymer chain (static nanofishing), where a polymer chain is picked up and pulled at its chemically modified terminals, only gives structural information such as persistence length and contour length. Beyond this technique, dynamic nanofishing, where an AFM cantilever is imposed on the forced oscillation at its resonant frequency (∼10 kHz), enables us to investigate more fruitful information. The method gave extension-dependent changes of entropic elasticity and frictional coefficient with solvent molecules for mono-disperse living-polymerized polystyrene (PS). The solvent temperature dependence revealed that the frictional coefficient could be correlated with macroscopic “intrinsic viscosity.” Another novel technique, nanofishing at fast pulling rate (fast nanofishing), exhibited internal entanglement of a single PS chain and its subsequent relaxation.

Experimental Studies of the Dynamic Mechanical Response of a Single Polymer Chain

2006 ◽  
Vol 39 (18) ◽  
pp. 6180-6185 ◽  
Author(s):  
Esben Thormann ◽  
Drew R. Evans ◽  
Vincent S. J. Craig
Keyword(s):  
Polymer Chain ◽  
Mechanical Response ◽  
Experimental Studies ◽  
Dynamic Mechanical ◽  
Single Polymer Chain

Construction of plastic contact deformation maps on ceramics: a case study on aluminum nitride

1996 ◽  
Vol 54 ◽  
pp. 636-637
Author(s):  
D. L. Callahan
Keyword(s):  
Plastic Deformation ◽  
Aluminum Nitride ◽  
Mechanical Response ◽  
Three Dimensional ◽  
Bright Field Image ◽  
Perfectly Plastic ◽  
Contrast Analysis ◽  
Deformation Patterns

Modern polishing, precision machining and microindentation techniques allow the processing and mechanical characterization of ceramics at nanometric scales and within entirely plastic deformation regimes. The mechanical response of most ceramics to such highly constrained contact is not predictable from macroscopic properties and the microstructural deformation patterns have proven difficult to characterize by the application of any individual technique. In this study, TEM techniques of contrast analysis and CBED are combined with stereographic analysis to construct a three-dimensional microstructure deformation map of the surface of a perfectly plastic microindentation on macroscopically brittle aluminum nitride.The bright field image in Figure 1 shows a lg Vickers microindentation contained within a single AlN grain far from any boundaries. High densities of dislocations are evident, particularly near facet edges but are not individually resolvable. The prominent bend contours also indicate the severity of plastic deformation. Figure 2 is a selected area diffraction pattern covering the entire indentation area.

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