• Steel and Composite Structures
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• v.32 no.5
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• pp.595-610
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• 2019

This paper deals with the static and dynamic behavior of Functionally Graded Carbon Nanotubes (FG-CNT)-reinforced porous sandwich (PMPV) polymer plate. The model of nanocomposite plate is investigated within the first order shear deformation theory (FSDT). Two types of porous sandwich plates are supposed (sandwich with face sheets reinforced / homogeneous core and sandwich with homogeneous face sheets / reinforced core). Functionally graded Carbon Nanotubes (FG-CNT) and uniformly Carbon Nanotubes (UD-CNT) distributions of face sheets or core porous plates with uniaxially aligned single-walled carbon nanotubes are considered. The governing equations are derived by using Hamilton's principle. The solution for bending and vibration of such type's porous plates are obtained. The detailed mathematical derivations are provided and the solutions are compared to some cases in the literature. The effect of the several parameters of reinforced sandwich porous plates such as aspect ratios, volume fraction, types of reinforcement, number of modes and thickness of plate on the bending and vibration analyses are studied and discussed. On the question of porosity, this study found that there is a great influence of their variation on the static and vibration of porous sandwich plate.

• Advances in aircraft and spacecraft science
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• v.9 no.1
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• pp.69-93
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• 2022

Reduced graphene oxide (rGO) is one of the derivatives of graphene, which has drawn some experimental research interests in recent years however, numerical research studying the mechanical behaviors of composites made of rGO has not been taken into consideration yet. The objective of this research is to investigate the buckling, and free vibration of functionally graded reduced graphene oxide reinforced nanocomposite (FG rGORC) plates employing isogeometric analysis (IGA). The effective Young's modulus of rGORC is determined based onthe Halpin-Tsai model. Four different FG distribution types of rGO are considered varying across plate thickness. Besides, the refined plate theory is used based on Reddy's third-order function. To capture the size effect, modified couple stress theory (MCST) is employed. A comprehensive study is provided examining the effect of various parameters including rGO weight fraction, FG distribution types, boundary conditions, material length scale parameter, etc. Our obtained results show that the addition of only 1% of uniformly distributed rGO into epoxy plates leads to the fundamental frequency and critical buckling load 18% and 39% higher than those of pure epoxy plates, respectively.

• Steel and Composite Structures
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• v.43 no.6
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• pp.725-734
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• 2022

In this paper, buckling analyses of nanocomposite plate reinforced by Graphen platelet (GPL) is studied. The Halphin-Tsai model is used for obtaining the effective material properties of nanocomposite plate. The nanocomposite plate is modeled by Third order shear deformation theory (TSDT). The elastic medium is simulated by Winkler model. Employing relations of strains-displacements and stress-strain, the energy equations of the plate are obtained and using Hamilton's principle, the governing equations are derived. The governing equations are solved based on analytical solution. The effect of GPL volume percent, geometrical parameters of plate and elastic foundation on the buckling load are investigated. Results show that with increasing GPLs volume percent, the buckling load increases. In addition, elastic medium can enhance the values of buckling load significantly.

• Polymer(Korea)
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• v.27 no.1
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• pp.75-83
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• 2003

Dicyanate-clay nanocomposite has been prepared by a melt in-situ polymerization method for different modifiers and cation exchange capacity (CEC) values in order to study dispersion and mechanical property. Various dicyanate nanocomposites were prepared by using different MMT systems containing different intercalants which led to different initial gallery heights and packing density. Depending on compatibility between dicyanate and clays, the degree of dispersion varied. Dispersion of clay plates in dicyanate resin depended mainly on CEC and aliphatic chain length of modifier. The lower CEC and shorter aliphatic chain length of modifier gave the exfoliation structure. It was also found that the reactivity of intercalant with dicyanate resin was one of the key factors facilitating the intercalation/exfoliation process of dicyanate/MMT nanocomposites. Shear modulus of reaction-induced dicyanate nanocomposite was significantly increased.

• Smart Structures and Systems
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• v.22 no.6
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• pp.743-751
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• 2018

In this project, buckling response of polymeric plates reinforced with carbon nanotubes (CNTs) and coated by magnetostrictive layer was studied. The equivalent nanocomposite properties are determined using Mori-Tanak model considering agglomeration effects. The structure is simulated with first order shear deformation theory (FSDT). Employing strains-displacements, stress-strain, the energy equations of the structure are obtained. Using Hamilton's principal, the governing equations are derived considering the coupling of mechanical displacements and magnetic field. Using Navier method, the buckling load of the sandwich structure is obtained. The influences of volume percent and agglomeration of CNTs, geometrical parameters and magnetic field on the buckling load are investigated. Results show that with increasing volume percent of CNTs, the buckling load increases. In addition, applying magnetic field, increases the frequency of the sandwich structure.

• Steel and Composite Structures
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• v.39 no.3
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• pp.275-290
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• 2021

The main purpose of this research work is to investigate the critical buckling load of functionally graded (FG) porous plates with graphene platelets (GPLs) reinforcement using generalized differential quadrature (GDQ) method at thermal condition. It is supposed that the GPL nanofillers and the porosity coefficient vary continuously along the plate thickness direction. Generally, the thermal distribution is considered to be nonlinear and the temperature changing continuously through the thickness of the nanocomposite plates according to the power-law distribution. To model closed cell FG porous material reinforced with GPLs, Halpin-Tsai micromechanical modeling in conjunction with Gaussian-Random field scheme are used, through which mechanical properties of the structures can be extracted. Based on the third order shear deformation theory (TSDT) and the Hamilton's principle, the equations of motion are established and solved for various boundary conditions (B.Cs). The fast rate of convergence and accuracy of the method are investigated through the different solved examples and validity of the present study is evaluated by comparing its numerical results with those available in the literature. A special attention is drawn to the role of GPLs weight fraction, GPLs patterns through the thickness, porosity coefficient and distribution of porosity on critical buckling load. Results reveal that the importance of thermal condition on of the critical load of FGP-GPL reinforced nanocomposite plates.

• Steel and Composite Structures
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• v.37 no.6
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• pp.711-731
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• 2020

This paper deals with free vibration of FG sandwich annular sector plates on Pasternak elastic foundation with different boundary conditions, based on the three-dimensional theory of elasticity. The plates with simply supported radial edges and arbitrary boundary conditions on their circular edges are considered. The influence of carbon nanotubes (CNTs) waviness, aspect ratio, internal pores and graphene platelets (GPLs) on the vibrational behavior of functionally graded nanocomposite sandwich plates is investigated in this research work. The distributions of CNTs are considered functionally graded (FG) or uniform along the thickness of upper and bottom layers of the sandwich sectorial plates and their mechanical properties are estimated by an extended rule of mixture. In this study, the classical theory concerning the mechanical efficiency of a matrix embedding finite length fibers has been modified by introducing the tube-to-tube random contact, which explicitly accounts for the progressive reduction of the tubes' effective aspect ratio as the filler content increases. The core of structure is porous and the internal pores and graphene platelets (GPLs) are distributed in the matrix of core either uniformly or non-uniformly according to three different patterns. The elastic properties of the nanocomposite are obtained by employing Halpin-Tsai micromechanics model. A semi-analytic approach composed of 2D-Generalized Differential Quadrature Method (2D-GDQM) and series solution is adopted to solve the equations of motion. The fast rate of convergence and accuracy of the method are investigated through the different solved examples. Some new results for the natural frequencies of the plate are prepared, which include the effects of elastic coefficients of foundation, boundary conditions, material and geometrical parameters. The new results can be used as benchmark solutions for future researches.

• Steel and Composite Structures
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• v.12 no.6
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• pp.491-504
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• 2012

In this paper, the nonlinear cylindrical bending of simply supported, functionally graded nanocomposite plates reinforced by single-walled carbon nanotubes (SWCNTs), is studied. The plates are subjected to uniform pressure loading in thermal environments and their geometric nonlinearity is introduced in the strain-displacement equations based on Von-Karman assumptions. The material properties of SWCNTs are assumed to be temperature-dependent and are obtained from molecular dynamics simulations. The material properties of functionally graded carbon nanotube-reinforced composites (FG-CNTCRs) are assumed to be graded in the thickness direction, and are estimated through a micromechanical model. The governing equations are reduced to linear differential equation with nonlinear boundary conditions yielding a simple solution procedure. Numerical results are presented to show the effect of the material distribution on the deflections and stresses.

• Steel and Composite Structures
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• v.35 no.1
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• pp.111-127
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• 2020

The goal of this study is to fill this apparent gap in the area about investigating the effect of porosity distributions on vibrational behavior of FG sectorial plates resting on a two-parameter elastic foundation. The response of the elastic medium is formulated by the Winkler/Pasternak model. The internal pores and graphene platelets (GPLs) are distributed in the matrix either uniformly or non-uniformly according to three different patterns. The model is proposed with material parameters varying in the thickness of plate to achieve graded distributions in both porosity and nanofillers. The elastic modulus of the nanocomposite is obtained by using Halpin-Tsai micromechanics model. The annular sector plate is assumed to be simply supported in the radial edges while any arbitrary boundary conditions are applied to the other two circular edges including simply supported, clamped and free. The 2-D differential quadrature method as an efficient and accurate numerical approach is used to discretize the governing equations and to implement the boundary conditions. The convergence of the method is demonstrated and to validate the results, comparisons are made between the present results and those reported by well-known references for special cases treated before, have confirmed accuracy and efficiency of the present approach. It is observed that the maximum vibration frequency obtained in the case of symmetric porosity and GPL distribution, while the minimum vibration frequency is obtained using uniform porosity distribution. Results show that for better understanding of mechanical behavior of nanocomposite plates, it is crucial to consider porosities inside the material structure.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.98-98
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• 2010

A epoxy/multilayered silicate nanocomposite was prepared by a new AC electric application method and micro silica particle was poured into the nanocomposite in order to prepare epoxy/micro-and-nano- mixed composites (EMNC). Electric insulation breakdown strength was measured in a sphere-sphere electrode system designed for the prevention of edge breakdown and the data were estimated by Weibull plot. As the exfoliated silicate nano-plates were homogeniously dispersed in the micro silica particles, the insulation property was higher.