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Papers by Majid Tavakolian

Research paper thumbnail of Nonlinear Vibration of Functionally Graded Cylindrical Shells under Radial Harmonic Load

Iranian Journal of Mechanical Engineering Transactions of the ISME, Sep 1, 2012

Research paper thumbnail of Numerical Simulation of Tensile Residual Stresses in SWCNT-Reinforced Polymer Composites

International Polymer Processing, Mar 1, 2021

The residual stresses play a significant role in the mechanical properties and strengthening capa... more The residual stresses play a significant role in the mechanical properties and strengthening capability of nanocomposites. The present research aims to numerically investigate the residual stress relaxation in nanotube-reinforced polymers in response to mechanical tensile loading. The systems under study consist of the armchair and zigzag single-walled carbon nanotubes (SWCNT) embedded in a polymer matrix. The nanotubes and polymer matrix are assumed to be bonded by van der Waals interactions based on the Lennard-Jones (L-J) potential at the interface. The interactions between carbon atoms in the nanotube and nodes in the polymer matrix are modelled by equivalent springs. In order to evaluate the analysis of elastic-perfectly plastic using finite element (FE) modelling, first, relaxation of the plastic residual stresses on steel hemisphere in contact with a rigid flat surface was examined in a loading-unloading cycle and verified with available data. Afterwards, the residual stress relaxation in nanotubes with different space-frame structures was computed due to displacement-controlled loading. Finally, the stress state and the plastic residual stresses in the nanocomposite for different carbon nanotube content were analyzed and discussed during loading and unloading. Regarding the effect of tensile stress, it was revealed that nanotube structures have significant effects on the residual stresses created in the nanocomposite.

Research paper thumbnail of Mechanical Properties of Nanoclay Reinforced Epoxy Adhesive Bonded Joints Made with Composite Materials

Journal of Adhesion Science and Technology, 2010

This article may be used for research, teaching, and private study purposes. Any substantial or s... more This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sublicensing, systematic supply, or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae, and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand, or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material.

Research paper thumbnail of Nonlinear vibration of functionally graded cylindrical shells embedded with a piezoelectric layer

Thin-Walled Structures, 2014

This paper addresses the nonlinear vibration problem of simply supported functionally graded (FG)... more This paper addresses the nonlinear vibration problem of simply supported functionally graded (FG) cylindrical shells with embedded piezoelectric layers. The governing differential equations of motion of the FG cylindrical shell are derived using the Lagrange equations under the assumption of the Donnell's nonlinear shallow-shell theory. A semi analytical approach, wherein the displacement fields are expanded by means of a double mixed series based on linear mode shape functions for the longitudinal, circumferential and radial variables, is proposed to characterize the nonlinear response of the cylindrical shell. The large-amplitude response and amplitude frequency curves of the cylindrical shell are obtained by using the proposed approach. Finally, the effects of excitation force and applied voltage on the vibration behavior of the cylindrical shell are investigated.

Research paper thumbnail of Molecular dynamics predictions of thermomechanical properties of an epoxy thermosetting polymer

Polymer, 2020

This paper reports the thermomechanical properties of a thermosetting polymer formed by curing a ... more This paper reports the thermomechanical properties of a thermosetting polymer formed by curing a DGEBA resin with a Jeffamine D230 agent predicted by molecular dynamics (MD) simulations. A multistep crosslinking approach is used to form the crosslinked network of the thermosetting polymer. The radial distribution function and X-ray diffraction pattern of the MD predicted crosslinked structure are calculated and compared with experimental results to validate the epoxy network system. Thermomechanical properties such as mass density, gel point, glass transition temperature (g), elastic moduli (Young's modulus and shear modulus), and yield strength in shear and tension are calculated at different temperatures and crosslinking conversions by employing the DREIDING and AMBER force fields. The MD predicted results are in good agreement with theoretical studies and existing experimental data. We find a significant increase in g and yield strength with crosslinking conversion. The elastic modulus is less sensitive to the strain rate, but the yield strength is significantly strain-rate dependent. The high-quality digital epoxy configurations developed in this work are available in LAMMPS data format from the journal website.

Research paper thumbnail of Free vibration analysis of functionally graded composite rectangular plates reinforced with graphene nanoplatelets (GPLs) using full layerwise finite element method

Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, Apr 17, 2023

Research paper thumbnail of Investigation of strain rate effects on the mechanical behavior of polymer nanocomposites with and without defects in nanotubes

Research paper thumbnail of A molecular dynamics study on the mechanical properties of defective CNT/epoxy nanocomposites using static and dynamic deformation approaches

International Polymer Processing, 2022

In this paper, the mechanical behavior of epoxy polymer nanocomposite with continuous single-wall... more In this paper, the mechanical behavior of epoxy polymer nanocomposite with continuous single-walled carbon nanotubes (SWCNT) with and without vacancy defects has been investigated based on two approaches of deformation, molecular mechanics (static) and molecular dynamics. In this regard, molecular simulation has been performed on the basis of the compass force field. In order to validate the research steps, the results obtained for pure epoxy polymer were compared with similar molecular dynamic simulations, which confirmed the simulation process. The research process proposed a method for controlling the symmetry of the system during equilibration with an asymmetric barostat. The Souza-Martins barostat was also used to apply loading and deformation control over a constant strain rate range. The results showed that in both deformation approaches (with and without calculating the contribution of kinetic energy), the presence of defects improved the transverse tensile and shear moduli,...

Research paper thumbnail of Correction to: Molecular dynamics predictions of thermo-mechanical properties of carbon nanotube/polymeric composites

International Nano Letters, 2021

A correction to this paper has been published: https://doi.org/10.1007/s40089-021-00336-y

Research paper thumbnail of Multi-scale Modeling and Damage Analysis of Carbon Nanotube–Carbon Fiber-Reinforced Polymeric Composites

Iranian Journal of Science and Technology, Transactions of Mechanical Engineering

Research paper thumbnail of Nonlinear Vibration of Functionally Graded Cylindrical Shells under Radial Harmonic Load

Iranian Journal of Mechanical Engineering Transactions of the ISME, Sep 1, 2012

Research paper thumbnail of Numerical Simulation of Tensile Residual Stresses in SWCNT-Reinforced Polymer Composites

International Polymer Processing, Mar 1, 2021

The residual stresses play a significant role in the mechanical properties and strengthening capa... more The residual stresses play a significant role in the mechanical properties and strengthening capability of nanocomposites. The present research aims to numerically investigate the residual stress relaxation in nanotube-reinforced polymers in response to mechanical tensile loading. The systems under study consist of the armchair and zigzag single-walled carbon nanotubes (SWCNT) embedded in a polymer matrix. The nanotubes and polymer matrix are assumed to be bonded by van der Waals interactions based on the Lennard-Jones (L-J) potential at the interface. The interactions between carbon atoms in the nanotube and nodes in the polymer matrix are modelled by equivalent springs. In order to evaluate the analysis of elastic-perfectly plastic using finite element (FE) modelling, first, relaxation of the plastic residual stresses on steel hemisphere in contact with a rigid flat surface was examined in a loading-unloading cycle and verified with available data. Afterwards, the residual stress relaxation in nanotubes with different space-frame structures was computed due to displacement-controlled loading. Finally, the stress state and the plastic residual stresses in the nanocomposite for different carbon nanotube content were analyzed and discussed during loading and unloading. Regarding the effect of tensile stress, it was revealed that nanotube structures have significant effects on the residual stresses created in the nanocomposite.

Research paper thumbnail of Mechanical Properties of Nanoclay Reinforced Epoxy Adhesive Bonded Joints Made with Composite Materials

Journal of Adhesion Science and Technology, 2010

This article may be used for research, teaching, and private study purposes. Any substantial or s... more This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sublicensing, systematic supply, or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae, and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand, or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material.

Research paper thumbnail of Nonlinear vibration of functionally graded cylindrical shells embedded with a piezoelectric layer

Thin-Walled Structures, 2014

This paper addresses the nonlinear vibration problem of simply supported functionally graded (FG)... more This paper addresses the nonlinear vibration problem of simply supported functionally graded (FG) cylindrical shells with embedded piezoelectric layers. The governing differential equations of motion of the FG cylindrical shell are derived using the Lagrange equations under the assumption of the Donnell's nonlinear shallow-shell theory. A semi analytical approach, wherein the displacement fields are expanded by means of a double mixed series based on linear mode shape functions for the longitudinal, circumferential and radial variables, is proposed to characterize the nonlinear response of the cylindrical shell. The large-amplitude response and amplitude frequency curves of the cylindrical shell are obtained by using the proposed approach. Finally, the effects of excitation force and applied voltage on the vibration behavior of the cylindrical shell are investigated.

Research paper thumbnail of Molecular dynamics predictions of thermomechanical properties of an epoxy thermosetting polymer

Polymer, 2020

This paper reports the thermomechanical properties of a thermosetting polymer formed by curing a ... more This paper reports the thermomechanical properties of a thermosetting polymer formed by curing a DGEBA resin with a Jeffamine D230 agent predicted by molecular dynamics (MD) simulations. A multistep crosslinking approach is used to form the crosslinked network of the thermosetting polymer. The radial distribution function and X-ray diffraction pattern of the MD predicted crosslinked structure are calculated and compared with experimental results to validate the epoxy network system. Thermomechanical properties such as mass density, gel point, glass transition temperature (g), elastic moduli (Young's modulus and shear modulus), and yield strength in shear and tension are calculated at different temperatures and crosslinking conversions by employing the DREIDING and AMBER force fields. The MD predicted results are in good agreement with theoretical studies and existing experimental data. We find a significant increase in g and yield strength with crosslinking conversion. The elastic modulus is less sensitive to the strain rate, but the yield strength is significantly strain-rate dependent. The high-quality digital epoxy configurations developed in this work are available in LAMMPS data format from the journal website.

Research paper thumbnail of Free vibration analysis of functionally graded composite rectangular plates reinforced with graphene nanoplatelets (GPLs) using full layerwise finite element method

Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, Apr 17, 2023

Research paper thumbnail of Investigation of strain rate effects on the mechanical behavior of polymer nanocomposites with and without defects in nanotubes

Research paper thumbnail of A molecular dynamics study on the mechanical properties of defective CNT/epoxy nanocomposites using static and dynamic deformation approaches

International Polymer Processing, 2022

In this paper, the mechanical behavior of epoxy polymer nanocomposite with continuous single-wall... more In this paper, the mechanical behavior of epoxy polymer nanocomposite with continuous single-walled carbon nanotubes (SWCNT) with and without vacancy defects has been investigated based on two approaches of deformation, molecular mechanics (static) and molecular dynamics. In this regard, molecular simulation has been performed on the basis of the compass force field. In order to validate the research steps, the results obtained for pure epoxy polymer were compared with similar molecular dynamic simulations, which confirmed the simulation process. The research process proposed a method for controlling the symmetry of the system during equilibration with an asymmetric barostat. The Souza-Martins barostat was also used to apply loading and deformation control over a constant strain rate range. The results showed that in both deformation approaches (with and without calculating the contribution of kinetic energy), the presence of defects improved the transverse tensile and shear moduli,...

Research paper thumbnail of Correction to: Molecular dynamics predictions of thermo-mechanical properties of carbon nanotube/polymeric composites

International Nano Letters, 2021

A correction to this paper has been published: https://doi.org/10.1007/s40089-021-00336-y

Research paper thumbnail of Multi-scale Modeling and Damage Analysis of Carbon Nanotube–Carbon Fiber-Reinforced Polymeric Composites

Iranian Journal of Science and Technology, Transactions of Mechanical Engineering