Composite Materials and Technology Center

Tehrān, Iran

Composite Materials and Technology Center

Tehrān, Iran

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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.


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.


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.


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.


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

In this work, the mechanical, rheological, and thermal properties and morphology of a polypropylene matrix reinforced with single-walled nanotubes (SWNTs) were investigated. Polypropylene-grafted-maleic acid was used as a compatibilizer to promote SWNTs dispersion. Compared to uncompatibilized nanocomposites, the tensile modulus of the material increased considerably when nanotubes and compatibilizer were employed. The rheological characterization results revealed that addition of SWNTs increased the storage modulus and complex viscosity at low frequencies. SEM revealed that the SWNTs were uniformly distributed when low concentrations of SWNTs were employed. The results of DSC indicated that the addition of SWNTs increased the crystallinity of nanocomposites. © 2012 Copyright Taylor and Francis Group, LLC.


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.


Jam J.E.,Composite Materials and Technology Center | Asghar A.P.,Composite Materials and Technology Center | Omidvar N.,Composite Materials and Technology Center
Journal of Computational and Theoretical Nanoscience | Year: 2014

This research is aimed at characterizing the elastic properties of carbon nanotubes (CNTs) reinforced composites using Eshelby-Mori-Tanaka approach based on an equivalent fiber. An embedded carbon nanotube in a polymer matrix and its surrounding interphase is replaced with an equivalent fiber for predicting the mechanical properties of the carbon nanotube/polymer composite. The inter-phase region is treated using van der Waals interactions. The properties of carbon nanotube reinforced (CNTR) composite are affected by its microstructure, especially the degree of CNT aggregation that is described by an aggregation coefficient. It is shown the degree of aggregation can seriously reduce the effective stiffness and frequency parameter. Copyright © 2014 American Scientific Publishers All rights reserved.


Maghamikia S.,Composite Materials and Technology Center | Jam J.E.,Composite Materials and Technology Center
Journal of Mechanical Science and Technology | Year: 2011

The critical compressive load in the buckling of circular and annular composite plates reinforced with carbon nanotubes (CNTs) is calculated using finite element method. The developed model is based on the third-order shear deformation theory for moderately thick laminated plates. Effects of CNTs orientation angles and thickness-to-inner radius ratio on the buckling of composite plates are discussed. The results are compared with those obtained by analytical method based on classical plate theory. The finite element method shows lower values for critical buckling load because of the elimination of shear strain in the classical plate theory. © 2011 The Korean Society of Mechanical Engineers and Springer-Verlag Berlin Heidelberg.


Maghamikia Sh.,Composite Materials and Technology Center | Jam J.E.,Composite Materials and Technology Center
Polymer Composites | Year: 2011

A micromechanics model is developed to calculate the effective elastic modulus of composite with aligned straight carbon nanotubes (CNTs). The interfacial bonding between CNTs and polymer matrix gives an important effect on reinforcing specification of CNTs. The nonlinear cohesive law is used to describe the interface debonding. The effect of debonding at CNTs/polymer interface and the van der Waal's (vdw) force between carbon atoms is studied on the mechanical properties of composite reinforced by CNTs. It is also shown that small CNTs have stronger reinforcing effect than larger ones. The debonded nanotubes behave like voids in the matrix and it can significantly reduce the stiffening effect of the nanocomposites. POLYM. COMPOS. © 2011 Society of Plastics Engineers.


Jam J.E.,Composite Materials and Technology Center | Asadi E.,Composite Materials and Technology Center
Archive of Mechanical Engineering | Year: 2012

In this paper, the authors investigate a cylindrical shell reinforced by carbon nanotubes. The critical buckling load is calculated using analytical method when it is subjected to compressive axial load. The Mori-Tanaka method is firstly utilized to estimate the effective elastic modulus of composites having aligned oriented straight CNTs. The eigenvalues of the problem are obtained by means of an analytical approach based on the optimized Rayleigh-Ritz method. There is presented a study on the effects of CNTs volume fraction, thickness and aspect ratio of the shell, CNTs orientation angle, and the type of supports on the buckling load of cylindrical shells. Furthermore the effect of CNTs agglomeration is investigated when CNTs are dispersed none uniformly in the polymer matrix. It is shown that when the CNTs are arranged in 90° direction, the highest critical buckling load appears. Also, the results are plotted for different longitudinal and circumferential mode numbers. There is a specific value for aspect ratio of the cylinder that minimizes the buckling load. The results reveal that for very low CNTs volume fractions, the volume fraction of inclusions has no important effect on the critical buckling load.

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