
text
article
2015
per
Journal of Science and Technology of Composites
Iran University of Science and Technology
23833823
2
v.
3
no.
2015
0
0
http://jstc.iust.ac.ir/article_15792_ca5649fc8ccf8669fc6a1a478fa848e7.pdf

text
article
2015
per
Journal of Science and Technology of Composites
Iran University of Science and Technology
23833823
2
v.
3
no.
2015
1
86
http://jstc.iust.ac.ir/article_15793_b25569ce1d37aaf4c6a18b55a5530d48.pdf
Exact micromechanical stress analysis of long fiber composites under uniform tensile loading
Hosein
Rahnama
School of Mechanical Engineering, Iran University of Science and Technology, Tehran, Iran
author
Mahmood Mehrdad
Shokrieh
Composite Research Lab., Center of Excellence in Experimental Solid Mechanics, School of Mechanical Engineering, Iran University of Science and Technology, Tehran, Iran
author
text
article
2015
per
In this paper, based on a systematic procedure in the field of theory of elasticity, it is tried to establish an exact closed form solution for the problem of a longfiber composite representative volume element (RVE) under uniform tension loading condition. To this end, the RVE of long fiber composites is considered. The RVE is composed of two concentric cylinders where the inner and outer ones are of fiber and matrix materials, respectively. Consequently, this study deals with an axially symmetric problem of the theory of elasticity. Using the Love function for axisymmetric problems, the Navier equilibrium equations for displacement components are converted to a single biharmonic equation in terms of the Love function. Then, a general expression for the separable solutions of biharmonic equation in cylindrical coordinates is derived. Next, according to the boundary conditions and physical interpretations, appropriate terms from separable solutions are chosen and a solution is suggested. In the final step, the unknown constants in the suggested solution are computed by using the boundary conditions. The obtained exact solution satisfies the entire field equations of theory of elasticity. Using this solution, the exact distribution of stress and displacement field components of the RVE is determined and related numerical results are presented. Based on the exact solution, an expression for the equivalent longitudinal modulus of composite is obtained and compared with the wellknown rule of mixture formula. This comparison reveals that the rule of mixture can be a good engineering approximation for the equivalent longitudinal modulus.
Journal of Science and Technology of Composites
Iran University of Science and Technology
23833823
2
v.
3
no.
2015
1
10
http://jstc.iust.ac.ir/article_15241_2e8f574c9ba733f4d40e38311010858a.pdf
Sliding contact between a rigid cylindrical punch and a functionally graded semiinfinite medium in the presence of a surface crack
Ali
Talezadehlari
Department of Mechanical Engineering, Amirkabir University, Tehran, Iran
author
Ali
Nikbakht
New Technologies Research Center, Amirkabir University, Tehran, Iran
author
Mojtaba
Sadighi
Department of Mechanical Engineering, Amirkabir University, Tehran, Iran
author
text
article
2015
per
In this article two dimensional sliding contact of a rigid cylindrical punch on a functionally graded (FG) semiinfinite medium is studied. The modulus of elasticity in the graded layer is calculated based on TTO model approximation. This model defines a parameter q which considers the microstructural interactions between the constituting phases. The governing equations are solved by finite difference (FD) method by means of MATLAB software. The effects of different parameters such as nonhomogeneity, q, the dimensions of the punch, the thickness of the graded layer and the coefficient of friction are investigated on the forcedisplacement diagram of the punch, stress distribution and modes I and II stress intensify factors (KI and KII). The results show that the contact force and the stress distribution under the punch are affected by the thickness of the graded layer, radius of the punch and the nonhomogeneity coefficient. But the variation of q has no effects on the contact force and the stress distribution under the punch. In the absence of the friction, KI is always nonpositive and the crack has no tendency to grow under this mode. Increasing the friction coefficient, increases KI but decreases KII.
Journal of Science and Technology of Composites
Iran University of Science and Technology
23833823
2
v.
3
no.
2015
11
22
http://jstc.iust.ac.ir/article_15136_8ade0854e24f4b70154e892014720d95.pdf
Damage analysis of holed composite laminates using continuum damage mechanics
Bijan
Mohammadi
School of Mechanical Engineering, Iran University of Science and Technology, Tehran, Iran.
author
Ali
Kazemi
School of Mechanical Engineering, Iran University of Science and Technology, Tehran, Iran.
author
Roohallah
Ghasemi
School of Mechanical Engineering, Iran University of Science and Technology, Tehran, Iran.
author
text
article
2015
per
In recent decades, continuum damage mechanics based models, has been of interest to researchers in the area of damage in composites. These models with considering the effects of damage on the mechanical properties of composites and without considering detailed phenomenon of the damage, can analyze wide range of failure modes, loadings and layups. The aim of this paper is to analyze holed composite laminates using continuum damage mechanics. The general damage theory that serves as the foundation for the model of this paper is the model proposed by Ladeveze, which involves damage and inelastic strains to estimate residual stiffness. The Ladeveze model is implemented in a user material defined subroutine of the ABAQUS software, to analyze four different laminate sequences of [02/902]s, [0/90/0/90]s, [452/452]s, and [0/90/45/45]s. The analysis includes initiation and growth of damage parameters, subsequently a parametric study for the influence of diameter of hole and the inelastic strain material constant in Ladeveze model. Hence, it was shown that increasing the hole diameter, reduces the laminate strength, while the inelastic strain material constant is proportional to transverse inelastic strains
Journal of Science and Technology of Composites
Iran University of Science and Technology
23833823
2
v.
3
no.
2015
22
34
http://jstc.iust.ac.ir/article_14845_d8ad8fbce71b833a43cdfe499b19c2ff.pdf
Postbuckling analysis of antisymmetric crossply composite plates under endshortening
Seyed Amir Mahdi
Ghannadpour
Department of New Technologies and Engineering, Shahid Beheshti University, G.C., Tehran, Iran
author
mohsen
barekati
Department of New Technologies and Engineering, Shahid Beheshti University, G.C., Tehran, Iran
author
text
article
2015
per
In this paper, a method based on Chebyshev polynomials is developed for examination of the postbuckling behaviour of thin rectangular antisymmetric crossply composite laminated plates with different boundary conditions under end shortening in their plane. Classical laminated plate theory is used for developing equilibrium equations that it produces acceptable results for thin plates. In this method, the equilibrium equations are solved directly by substituting the displacement fields with equivalent finite Chebyshev polynomials. Using this method allows developing the mathematical model of composite laminated plates with different boundary conditions on all edges. Equations system is introduced by discretizing equilibrium equations and boundary conditions with finite Chebyshev polynomials. Nonlinear terms caused by the product of variables are linearized by using quadratic extrapolation technique to solve the system of equations. Since number of equations is always more than the number of unknown parameters, the least squares technique is used to solve the system of equations. Some results for antisymmetric crossply composite plates under endshortening in their plane with different boundary conditions are computed and compared with those available in the literature, wherever possible.
Journal of Science and Technology of Composites
Iran University of Science and Technology
23833823
2
v.
3
no.
2015
35
42
http://jstc.iust.ac.ir/article_15135_f7866b9260e7bbd78a8c461ef12bb92d.pdf
Analysis of interlaminar stresses in crossply composite cylinders subjected to radial loads
Isa
Ahmadi
Center of Computational Mechanics, Department of Mechanical Engineering, University of Zanjan, Zanjan, Iran
author
text
article
2015
per
In this study, the stress field and specially the interlaminar stresses in a composite cylinder with finite length which is subjected to radial load are studied. The displacement based layerwise theory (LWT) of Reddy is used for formulation and solution of a composite cylinder which is subjected to internal and external pressure. The principle of minimum total potential energy is used to derive the governing equations and the appropriate boundary conditions (BC) for the problem. The governing equations of the problem include a set of coupled ordinary differential equations in the terms of the unknown displacement functions of the mathematical surfaces in the LWT. A set of new variables are defined and the governing equations of the problem are solved analytically. The free edge boundary conditions are considered in the analysis. In the numerical results, the distribution of the interlaminar stresses and inplane stresses in the symmetric and unsymmetric laminated composite cylinders which are subjected to internal or external pressure are presented. It is seen that the layer stacking has important effect on the distribution and magnitude of the interlaminar stresses in the cylinder. It is observed that the maximum value of the interlaminar normal stresses in the free edge of the cylinder is bigger than the applied radial pressure and the interlaminar shear stress is in the order of the applied pressure.
Journal of Science and Technology of Composites
Iran University of Science and Technology
23833823
2
v.
3
no.
2015
43
54
http://jstc.iust.ac.ir/article_15240_14228fd251cdd291bc79fb334a65e23c.pdf
Analytical solution for free vibration of functionally graded carbon nanotubes (FGCNT) reinforced doublelayered nanoplates resting on elastic medium
Mohammad
HeidariRarani1
Department of Mechanical Engineering, Faculty of Engineering, University of Isfahan, Isfahan, Iran
author
Sajad
Alimirzaei
Department of Mechanical Engineering, University of Kashan, Kashan, Iran
author
Keivan
Torabi
Department of Mechanical Engineering, University of Kashan, Kashan, Iran
author
text
article
2015
per
In this paper, free vibration of an embedded doublelayered nanoplate reinforced by functionally graded carbon nanotubes (FGCNT) is analytically investigated. Carbon nanotubes are distributed through the thickness in two ways: uniform distribution and symmetrically linear distribution (or decreasingincreasing layup). To accurately model this nanocomposite behavior, the elastic medium around the nanoplate is modeled by Pasternak elastic foundation and the Van der waals forces between two nanoplates are taken into account. Governing equations of motions are obtained using energy method in association with Eringen nonlocal theory and solved by Navier method for a simplysupported rectangular plate. Finally, the effect of elastic foundation parameters, different distributions of CNT and nonlocal parameters are investigated on the vibration behavior of orthotropic doublelayer nanoplate. Results show that natural frequencies of a doublelayer nanoplate increase by increasing the Winkler elastic constants while Pasternak elastic constant has less effect on the results. Also, increasing the nonlocal parameter at a constant length decreases the natural frequencies. By increasing the length to thickness ratio (L/h) of nanoplate, the nonlocal frequencies reduce and natural frequency of symmetrically linear distribution is more than those of uniform distribution for constant value of L/h.
Journal of Science and Technology of Composites
Iran University of Science and Technology
23833823
2
v.
3
no.
2015
55
66
http://jstc.iust.ac.ir/article_15196_255575875e7c643fae978eb431615579.pdf
Experimental investigation of mechanical properties of injected polymeric nanocomposites containing multiwalled carbon nanotubes according to design of experiments
Parastoo
Esmaili
Department of Mechanical Engineering, Urmia University, Urmia, Iran
author
Taher
Azdast
Department of Mechanical Engineering, Urmia University, Urmia, Iran
author
Ali
Doniavi
Department of Mechanical Engineering, Urmia University, Urmia, Iran
author
Rezgar
Hasanzadeh
Department of Mechanical Engineering, Urmia University, Urmia, Iran
author
Sajad
Mamaghani
Department of Mechanical Engineering, Urmia University, Urmia, Iran
author
Richard
Eungkee Lee
Macro Engineering and Technology Inc., Mississauga, Ontario, Canada
author
text
article
2015
per
In present study, the tensile strength and hardness of polymeric nanocomposites containing multiwalled carbon nanotubes (MWCNT) are investigated. For this purpose, polyamide6 and MWCNTs in various weight percentages are melt compounded using a twinscrew extruder. To investigate the influence of MWCNTs and injection molding processing parameters on tensile strength and hardness, the samples in various MWCNT contents including 0, 0.5, 1 and 1.5 weight percentages and under different processing parameters including holding pressure and injection temperature, are injection molded according to Taguchi design of experiments. According to the results of signal to noise (S/N) ratio, the weight percentage of MWCNT is the most effective parameter on the tensile strength and hardness of samples. Also, the results indicate that by adding 1 wt% of MWCNT, the tensile strength of samples increased almost 31% and by addition of 1.5 wt% MWCNT, the hardness increased about 15%. Furthermore The results of analysis of variance (ANOVA) indicates that wt% of MWCNT with 68% and 76% contribution percentage on tensile strength and hardness of samples, are the most effective processing parameters, respectively.
Journal of Science and Technology of Composites
Iran University of Science and Technology
23833823
2
v.
3
no.
2015
67
74
http://jstc.iust.ac.ir/article_15197_f0312a77a8cdf8dc8de09ff30118023c.pdf
MeltSolidGas behavior in the interface of Al/Mg composite produced by centrifugal casting
Morteza
Sarvari
Department of Material, Iran University of Science and Technology, Tehran, Iran
author
Mehdi
Divandari
Department of Material, Iran University of Science and Technology, Tehran, Iran
author
text
article
2015
per
Al/Mg composite have new applications in various industries such as car manufacturing and aerospace. In this work characteristic of metallurgical interface and the behavior of meltsolidgas during production of Al/Mg composite via vertical centrifugal casting process was investigated Aluminium melt, at 700 oC and volume ratio of nearly one, was poured into a solid Mg rings preheated up to 30, 100, 150 and 200 oC, respectively while rotating at 1200 rpm, in a vertical centrifugal casting machine. After casting samples were cut and interfacial microstructure was studied by optical and scanning electron microscopes. Results show that the heat content of Al melt lead to dissolving preference prominent locations and creating local Mg rich regions. Study of the Al/Mg interface also showed that intermetallic compounds, Al3Mg2, Al12Mg17 are formed. Furthermore, gas pores may form, on notches present on the rough surface of the solid Mg ring, possibly as a result of melt/gas reaction. Possible states and conditions of the formation of bubble and gas porosity are discussed.
Journal of Science and Technology of Composites
Iran University of Science and Technology
23833823
2
v.
3
no.
2015
75
82
http://jstc.iust.ac.ir/article_14905_2db575da48558fad8386745cd678b3b8.pdf