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1

Elastic moduli of carbon nanotubes with new geometry based on FEM

Fereidoon A., Rajabpour M., Hemmatian H.

Journal of Theoretical and Applied Mechanics

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2014

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Vol. 52 nr 1

235--245

EN

In this paper, the elastic moduli of elliptic single walled carbon nanotubes (ESWCNTs) are described. A three-dimensional finite element (FE) model for such carbon nanotubes is proposed. The covalent bonds are simulated by beam elements in the FE model. The elastic moduli of beam elements are ascertained from a linkage between molecular and continuum mechanics. The deformations of the FE model are subsequently used to predict the elastic moduli of ESWCNTs. In order to demonstrate the FE performance, the influence of length, chirality, diameter and cross sectional aspect ratios on the elastic moduli (Young’s modulus and shear modulus) of ESWCNTs is investigated. It is found that the cross sectional aspect ratio of ESWCNTs significantly affects the elastic moduli. With increasing cross sectional aspect ratio, the Young’s modulus and shear modulus decrease. As a result, every change in geometry operates as a defect and decreases the elastic moduli. With increasing the length, Young’s modulus increases and the shear modulus decreases.

2

Modeling of polymer/clay nanocomposites by an iterative micromechanical approach

Mohyeddin A., Fereidoon A.

Archives of Mechanics

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2012

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Vol. 64, nr 6

541-554

EN

An iterative micromechanical method is presented in order to predict the elastic constants of composites and nanocomposites including arbitrarily oriented reinforcement particles. The proposed method is capable of introducing into the matrix any kind of heterogeneity based on its dimension, orientation, mechanical properties and volume fraction. The efficiency and convergence of solution method is studied by computing the elasticity tensor of a unidirectional particulate composite. It is then applied to model the elastic behavior of nylon-6/clay nanocomposite with taking into consideration the probability distribution of aspect ratio and orientation of effective particles. The results are validated by comparison with available experimental data.

3

Application of generalized differential quadrature method to nonlinear bending analysis of a single SWCNT over a bundle of nanotubes

Fereidoon A., Babaee A. M., Rostamiyan Y.

Archives of Mechanics

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2012

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Vol. 64, nr 4

347-366

EN

The deformation of an individual single walled carbon nanotube (SWCNT) over a bundle of nanotubes has been studied using the generalized differential quadrature (GDQ) method. The effects of length, diameter, and minimum value of Lennard–Jones experimental potential have been considered in the governing equation which is derived based on the GDQ and the issues related to the implementation of the boundary and compatibility conditions were addressed. The explanation of reliability and flexibility of the GDQ is done by solving several selected examples which are evaluated by comparing them with existing exact or approximate solutions which were previously generated by finite element approach.

4

Nonlinear analysis of functionally graded beams

Tahani M., Torabizadeh M. A., Fereidoon A.

Journal of Achievements in Materials and Manufacturing Engineering

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2006

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Vol. 18, nr 1-2

315--318

EN

Purpose: It is the intention of the present study to examine the effect of geometric nonlinearity on displacements and stresses in beams made of functionally graded materials (FGMs) subjected to thermo-mechanical loadings. Design/methodology/approach: The nonlinear strain-displacement relations are used to study the effect of geometric nonlinearity. Temperature distribution through the thickness of the beams in thermal loadings is obtained by solving the one-dimensional heat transfer equation. Then the equilibrium equations are obtained within the framework of the first-order shear deformatyion beam theory (FSDBT) and then solved exactly and also by using a perturbation technique. The results obtained from these two methods are compared for various loadings and boundary conditions. Findings: The numerical results showed that the nonlinearity effect on the displacements and stresses of the beams is significant. Also the effects of material constant n and the boundary conditions on the nonlinear bending behavior of the beams are determined. Research limitations/implications: The exact solution method of nonlinear equilibrium equations can only be developed for composite beams with the same boundary conditions at the ends. Practical implications: It is showed that for the maximum deflections greater than 0.3h a nonlinear solution is required. Originality/value: The paper introduces a new method to obtain analytical solution for nonlinear equilibrium equations. This method can be used in developing higher-order shear deformation and layerwise theories.