محمد اسماعیل گلمکانی

In this research, the mechanical behavior of composites made with polyethylene matrix and wood powder reinforcement have been investigated. In order to improve the mechanical properties, the wood powder has been added to polyethylene at three levels of 30, 40 and 50 wt.%. The material was mixed using an internal mixer Haake and then the material was removed from the mixer and was granulated by a crushing machine. Finally, the granules were molded using an injection molding machine and tensile test specimens were made according to ASTM D638 standard and bending test specimens were made according to ASTM D790 standard. After preparing the specimens, a tensile and flexural test performed on them. The results of the mechanical tests show that the amount of elastic modulus increased with increasing the amount of wood powder so that the highest amount of elastic modulus was observed in the specimens containing 50 wt.% wood powder. Also, the highest strength in the tensile test was observed at the level of 30 wt.% of the wood weight and the highest flexural strength was in the 50% level of wood weight. Also, mechanical tests were simulated using Abaqus software.

In this study, nonlinear bending analysis of functionally graded carbon nanotube reinforced composite (FG-CNTRC) cylindrical panels subjected to a uniform transverse mechanical load and thermal gradient along the radial direction is investigated. The equilibrium equations are derived based on first-order shear deformation shell theory (FSDT) and nonlinear von karman strains. Four types of uniform and functionally graded distributions of the reinforcement along the thickness direction of panels are considered. The nonlinear coupled equations of motion are solved by combination of dynamic relaxation (DR) and finite difference methods for different combinations of simply supported and clamped boundary conditions. In order to verify the current work, some obtained results are compared with the solutions reported in the literature and also ABAQUS finite element packages. In the presented parametric study, the effects of distribution of carbon nanotubes (CNTs), thickness-to-radius and length-to-radius ratios, boundary conditions, volume fraction of CNTs and panel angel is considered on the deflection and stress resultants in detail. The results show that FG-O and FG-X distributions of CNTs have the maximum and minimum values of deflection, respectively, for both simply supported and clamped boundary conditions.

In this study, nonlinear axisymmetric bending analysis of Functionally Graded Carbon Nanotube Reinforced Composite (FG-CNTRC) cylindrical shell is investigated. Four distribution types of carbon nanotubes along the thickness direction of shells are considered, including a uniform and three kinds of functionally graded distributions. The material properties of FG-CNTRC shells are determined according to the modified rule of mixture. The equilibrium equations are derived based on First-order Shear Deformation Shell Theory (FSDT) and nonlinear Donnell strains. The coupled nonlinear governing equations are solved by Dynamic Relaxation (DR) method combined with central finite difference technique for different combinations of simply supported and clamped boundary conditions. For this purpose, a FORTRAN computer program is provided to generate the numerical results. In order to verify the accuracy of the formulation and present method, the results are compared with those available in the literatures for ABAQUS finite element package, as well as a similar report for an isotropic function shell. The appropriate accordance of the results indicated the accuracy of employed numerical solution in the present study. Finally, a parametric study is carried out to study the effects of distribution of carbon nanotubes (CNTs), shell radius and width-to-thickness ratios, boundary conditions and volume fraction of CNTs on the deflection, stress and moment resultants in detail. The results show that with increase of CNTS volume fractions, the O and UD distributions have the most and the least decrease of deflection, respectively, in both clamped and simply supported boundary conditions.

The main purpose of this study is to investigate the nonlinear bending and buckling analysis of radially functionally graded sector plates subjected to uniform in-plane compressive loads. The mechanical properties of plates assumed to vary continuously along the radial direction by the Mori–Tanaka distribution. The incremental form of nonlinear formulations are derived based on first order shear deformation theory (FSDT) and large deflection von Karman equations. The dynamic relaxation (DR) method combined with the finite difference discretization technique is employed to solve the equilibrium equations. Also, due to the lack of similar research for the buckling of functionally graded sector plates with material variation in the radial direction, some results are compared with the ones reported by the ABAQUS finite element software. The achieved good agreements between the results indicate the accuracy of the present numerical method. Finally, numerical results for the maximum displacement and critical buckling load for various boundary conditions, effects of grading index, thickness-to-radius ratio, sector angle and inner radius-to-outer radius ratio are presented.

In this paper, buckling behavior of functionally graded carbon nanotube-reinforced composite (FG-CNTRC) plates is studied in line with the plates thikness. All governing equations are presented incrementally, based on a First-order Shear Deformation Theory (FSDT) of plates and von Karman strain field. In order to find the critical buckling load, the axial load is applied to the plate incrementally and the equilibrium equations are solved by Dynamic Relaxation (DR) method. Parametric study of the effects of volume fraction of Carbon Nanotubes (CNTs), CNTs distribution, plate width-to-thickness ratio and aspect ratio of nano composite plates is done in detail. The results show that functionally graded distribution of CNTs causes a significant increase of critical buckling load.

The main purpose of this study is to investigate nonlinear buckling analysis of Functionally Graded (FG) cylindrical shells under uniform axial compressive loads by dynamic relaxation (DR) method. The mechanical properties of shell vary continuously throughout the thickness direction according to the power-law، exponential function and the Mori-Tanaka distribution. The poisson’s ratio of the FG cylindrical shell is constant for power-law and exponential function. But in the Mori-Tanaka distribution variations of poisson''s ratio is determined as a function of the thickness direction. The incremental form of nonlinear formulations are based on first order shear deformation theory (FSDT) and large deflection von Karman equations. The DR method combined with the finite difference discretization technique is employed to solve the equilibrium equations. Some comparison study is carried out to compare the current solution with the results reported in the literature and the ones obtained by the Abaqus finite element software for the isotropic cylindrical shells. Finally، numerical results are presented for critical buckling load with various boundary conditions، grading indices، radius -to- thickness ratio، length -to- radius ratio and variation of poisson’s ratio.

Nonlinear bending of a functionally graded nanocomposite plate reinforced by aligned and straight single-walled carbon nanotubes (SWCNTs) subjected to a uniform transverse load and thermal load is investigated. The material properties of the nanocomposite plate are assumed to be graded in the thickness direction، Four types of distributions of the reinforcement material are considered، that is، uniform and three kinds of functionally graded distributions of carbon nanotubes along the thickness direction of plates. The material properties of SWCNT are determined according to molecular dynamics (MDs)، and then the effective material properties at a point are estimated according to the rule of mixture. The equilibrium equations are based on first-order shear deformation plate theory (FSDT) and von Kármán strains. These system of equations are solved by Dynamic Relaxation method to determine the load-deflection and load-bending moment curves. Some results for nanocomposite plates are compared with the ones reported by the ABAQUS finite element software. Furthermore، some comparison study is carried out to compare the current solution with the results reported in the literature for isotropic and Functionally Graded Materials (FGMs) plates. Numerical results indicate that volume fraction of carbon nanotube، distribution of CNTs، plate width-to-thickness ratio، plate aspect ratio and different boundary condition have pronounced effects on the nonlinear response of nanocomposite plates.

In this article، nonlinear axisymmetric bending analysis of sandwich circular plates with homogeneous face sheet and functionally graded core subjected to thermo - mechanical loads is presented. The formulations are based on first-order shear deformation plate theory (FSDT) and large deflection von Karman equations. The nonlinear equilibrium equations are solved using the dynamic relaxation (DR) method combined with the finite difference discretization technique. Material properties are compare to be temperature-dependent and temperature-independent. In order to verify the current work some obtained results are compared with Abaqus finite element method. Finally، The influences of material grading index، boundary conditions،tempresure، core-to-face sheets thickness ratio on the results are studied in detail. Also، in order to investigate the differences between the linear and nonlinear solutions some results are presented based on both linear and nonlinear analysis. Some results indicate that variation of core-to-face sheets thickness ratiohas greater effect on the results of annular geometry compared to circular one.

In this article، nonlinear bending analysis of sandwich circular plates with functionally graded face sheets subjected to transverse mechanical load is presented. The formulations are based on first-order shear deformation plate theory (FSDPT) and large deflection von Karman equations and nonlinear equilibrium equations solved by the dynamic relaxation (DR) method combined with the finite difference discretization technique. In order to verify the current work some obtained results are compared with the solutions reported in the literature and Abaqus finite element method. Finally، The influences of material constant k، boundary conditions، core-to-face sheets thickness ratio on the results are studied in detail.

In this paper، nonlinear bending of rectangular nanoplates of Graphene subjected to a transverse uniform load، with incorporation of the nonlocal effect of Eringen based on the first-order shear deformation theory (FSDT) of orthotropic plates and Von Karman nonlinear strains is investigated using differential quadrature method (DQM). In order to validate of the solution accuracy، the simplified results have been compared with results of two developed numerical solution methods and other available results. Comparisons show an excellent agreement between the results. Finally، effects of small scale parameter، aspect ratio، thickness of plate، load value، boundary conditions and efficacy of large deflection، on the maximum deflection and different deflections ratio for nonlocal theory of thin plate and nonlocal FSDT are investigated. Results reveal that among the considered parameters، just aspect of plate is the parameter of difference between two employed nonlocal theories and the small scale parameter has not any effect on the mentioned difference. Also، it is found that the small scale parameter has a noticeable effect on the decrease of deflection of nonlinear solution; so that، unlike the larger values of mechanical load، this parameter has less effect for long length of square plate.

In this study, nonlinear bending analysis of ring-stiffened annular laminated composite plates is studied. A discretely stiffened plate theory for elastic large deflection analysis of uniformly distributed loaded is introduced. The governing equations are derived based on a first-order shear deformation plate theory (FSDT) and large deflection von Karman equations. The numerical results are obtained using the dynamic relaxation (DR) method combined with the central finite difference discretization technique. For this purpose, a FORTRAN computer program is developed to generate the numerical results. In order to verify the accuracy of the present method the results are compared with those available in the literatures and ABAQUS finite element package as well. The computer code can handle symmetric, unsymmetrical and general theta-ply schemes. The effects of the plate thicknesses, different ratio of outer to inner radius, depth of stiffener, boundary condition and laminates lay-up are studied in detail.

The main purpose of this study is to investigate nonlinear bending and buckling analysis of radially functionally graded annular plates subjected to uniform in-plane compressive loads by Dynamic Relaxation method. The mechanical properties of plates assumed to vary continuously along the radial direction by the Mori–Tanaka distribution. The nonlinear formulations are based on first order shear deformation theory (FSDT) and large deflection von Karman equations. The dynamic relaxation (DR) method combined with the finite difference discretization technique is employed to solve the equilibrium equations. Due to the lack of similar research for the bending and buckling of functionally graded annular plates with material variation in the radial direction، some results are compared with the ones obtained by the Abaqus finite element software. Furthermore، some comparison study is carried out to compare the current solution with the results reported in the literature for annular isotropic plates. The achieved good agreements between the results indicate the accuracy of the present numerical method. Finally، numerical results for the maximum displacement and critical buckling load for various boundary conditions، effects of grading index، thickness-to-radius ratio and inner radius -to-outer radius ratio are presented.

In this paper، static bending behavior of square orthotropic nanoplate of Graphene، embedded in elastic matrix has been investigated. Based on first-order shear deformation theory of plates and strain-displacement relationships for small deflection theory the equilibruim equatuions are derived. Also، nonlocal continuum theory of Eringen is employed as implementation the small scale effect. Then equilibrium equations are rewrite at displacement parameter and after normalizing، are discretized and solved by differential quadrature and finite difference methods. with comparison study between the results of the mentioned theories، the accuracy and reliability of the present soulotion methodology is verified. Finally، maximum value of deflection has been peresented and influences of the small scale coefficient، width ratio، thickness of plate، load value، elastic matrix properties and mesh point numbers are investigated based on of first-order shear deformation and classical theories. It is concluded that with increase of small scale effects، the values of deflections decrease significantly.