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Jam J.E.,Composite Materials and Technology Center | Pourasghar A.,Islamic Azad University at Tehran | Kamarian S.,Razi University
Polymer Composites | Year: 2012

In this study, based on the three-dimensional theory of elasticity, free vibration characteristics of nanocomposite cylindrical panels reinforced by single-walled carbon nanotubes (CNTs) are considered. The carbon nanotube-reinforced (CNTRC) cylindrical panel has smooth variation of CNT fraction in the radial direction, and the material properties are estimated by the extended rule of mixture. In this work, 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. Symmetric and asymmetric volume fraction profiles are provided in this work for comparison. Suitable displacement functions that identically satisfy the boundary conditions at the simply supported edges are used to reduce the equilibrium equations to a set of coupled ordinary differential equation with variable coefficients, which can be solved by a generalized differential quadrature method. The results show that the kind of distribution and volume fraction of CNT have a significant effect on normalized natural frequency.POLYM. COMPOS., 33:2036-2044, 2012. © 2012 Society of Plastics Engineers Copyright © 2012 Society of Plastics Engineers. Source

Jam J.E.,Composite Materials and Technology Center | Kiani Y.,Amirkabir University of Technology
Composite Structures | Year: 2015

Response of functionally graded carbon nanotube reinforced composite (FG-CNTRC) beam subjected to the action of an impacting mass is analyzed. Timoshenko beam theory is used to estimate the kinematics of the beam. Material properties of the fibers and polymeric matrix are assumed to be temperature dependent. Both uniform and functionally graded distribution of CNTs are taken into account. Material properties of the composite are obtained using a refined rule of mixture. Contact force between the impactor and the beam is obtained with the aid of the conventional Hertz law. The governing dynamic equations of the system, are obtained using the conventional polynomial Ritz method applied to the total energy of the system. The solution of the resulting equations is traced in time using the well-known Runge-Kutta method. After examining the validity of the present solution, parametric studies are conducted to examine the influences of thermal environment, volume fraction of the CNTs, distribution of CNTs, initial velocity of the impactor and the impactor mass. Numerical results reveal that as the volume fraction of CNTs increases in the beam, peak contact force increases and the contact time decreases. Furthermore, temperature rise results in higher contact time duration and lower peak contact force. © 2015 Elsevier Ltd. Source

Jam J.E.,Composite Materials and Technology Center | Kiani Y.,Amirkabir University of Technology
Composite Structures | Year: 2015

A linear buckling analysis is presented for nanocomposite conical shells reinforced with single walled carbon nanotubes (SWCNTs) subjected to lateral pressure. Material properties of functionally graded carbon nanotube reinforced composite (FG-CNTRC) conical shell are assumed to be graded across the thickness and are obtained based on the modified rule of mixture. Governing equilibrium equations of the shell are obtained based on the Donnell shell theory assumptions consistent with the first order shear deformation shell theory. General form of the equilibrium equations and the complete set of boundary conditions are obtained based on the concept of virtual displacement principle. Shell is assumed to be under lateral pressure. Prebuckling load of the shell is estimated based on the linear membrane analysis. Stability equations of the shell are extracted via the adjacent equilibrium criterion. Resulting stability equations are discreted by suitable trigonometric functions in circumferential direction and generalized differential quadrature method in axial direction. An eigenvalue problem is established to obtain the buckling pressure and circumferential buckling mode of the conical shell. It is shown that, CNTs volume fraction and CNTs distribution law are important factors on the buckling mode and buckling load of the FG-CNTRC conical shells. © 2015 Elsevier Ltd. Source

Jam J.E.,Composite Materials and Technology Center | Pourasghar A.,Islamic Azad University at Tehran | Kamarian S.,Composite Materials and Technology Center | Maleki Sh.,Composite Materials and Technology Center
Polymer Composites | Year: 2013

Effective elastic properties for carbon nanotube (CNT)-reinforced composites are obtained through a variety of micromechanics techniques. An embedded CNT in a polymer matrix and its surrounding interphase is replaced with an equivalent fiber for predicting the mechanical properties of the CNT/polymer composite. Formulas to extract the effective material constants from solutions for the representative volume element under three loading cases are derived based on the elasticity theory. The effects of an interphase layer between the nanotubes and the polymer matrix as result of effective interphase layer are also investigated. Furthermore, this research is aimed at characterizing the elastic properties of CNTs-reinforced composites using Eshelby-Mori-Tanaka approach based on an equivalent fiber. The variations of mechanical properties with tube radius, interphase thickness, and degree of aggregation are investigated. It is shown that the presence of aggregates has stronger impact than the interphase thickness on the effective modulus of the composite. This is because aggregates have significantly lower modulus than individual CNTs. © 2013 Society of Plastics Engineers. Source

Jam J.E.,Composite Materials and Technology Center | Ahangari M.,Composite Materials and Technology Center
Polymer - Plastics Technology and Engineering | Year: 2012

The rheological and electrical percolation of single-walled carbon nanotubes on a thermoplastic-elastomer based on polypropylene/ethylene-propylene-diene was investigated. Polypropylene-grafted maleic anhydride was used to improve the nanotube dispersion. The shear stress and viscosity decreased with increasing temperature from 200 to 220°C. The flow activation energy for the nanocomposites increased with increasing nanotube content. The morphology and degree of dispersion of the nanotubes in the thermoplastic-elastomer matrix were investigated using SEM. The obtained rheological and electrical properties of the nanocomposites indicate that they were affected by the nanotube-nanotube network structure, which was related to the morphological behavior of nanotubes uniform dispersion. © 2012 Copyright Taylor and Francis Group, LLC. Source

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