• Title/Summary/Keyword: nanocomposite structures

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Structural and Thermal Analysis and Membrane Characteristics of Phosphoric Acid-doped Polybenzimidazole/Strontium Titanate Composite Membranes for HT-PEMFC Applications

  • Selvakumar, Kanakaraj;Kim, Ae Rhan;Prabhu, Manimuthu Ramesh;Yoo, Dong Jin
    • Composites Research
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    • v.34 no.6
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    • pp.373-379
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    • 2021
  • A series of novel PBI/SrTiO3 nanocomposite membranes composed of polybenzimidazole (PBI) and strontium titanate (SrTiO3) with a perovskite structure were fabricated with various concentrations of SrTiO3 through a solution casting method. Various characterization techniques such as proton nuclear magnetic resonance, thermogravimetric analysis, atomic force microscopy (AFM) and AC impedance spectroscopy were used to investigate the chemical structure, thermal, phosphate absorption and morphological properties, and proton conductivity of the fabricated nanocomposite membranes. The optimized PBI/SrTiO3-8 polymer nanocomposite membrane containing 8wt% of SrTiO3 showed a higher proton conductivity of 7.95 × 10-2 S/cm at 160℃ compared to other nanocomposite membranes. The PBI/SrTiO3-8 composite membrane also showed higher thermal stability compared to pristine PBI. In addition, the roughness change of the polymer composite membrane was also investigated by AFM. Based on these results, nanocomposite membranes based on perovskite structures are expected to be considered as potential candidates for high-temperature PEM fuel cell applications.

Dynamic analysis of functionally graded nanocomposite plates reinforced by wavy carbon nanotube

  • Moradi-Dastjerdi, Rasool;Momeni-Khabisi, Hamed
    • Steel and Composite Structures
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    • v.22 no.2
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    • pp.277-299
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    • 2016
  • In this paper, free vibration, forced vibration, resonance and stress wave propagation behavior in nanocomposite plates reinforced by wavy carbon nanotube (CNT) are studied by a mesh-free method based on first order shear deformation theory (FSDT). The plates are resting on Winkler-Pasternak elastic foundation and subjected to periodic or impact loading. The distributions of CNTs are considered functionally graded (FG) or uniform along the thickness and their mechanical properties are estimated by an extended rule of mixture. In the mesh-free analysis, moving least squares (MLS) shape functions are used for approximation of displacement field in the weak form of motion equation and the transformation method is used for imposition of essential boundary conditions. Effects of CNT distribution, volume fraction, aspect ratio and waviness, and also effects of elastic foundation coefficients, plate thickness and time depended loading are examined on the vibrational and stresses wave propagation responses of the nanocomposite plates reinforced by wavy CNT.

Transient heat transfer analysis of functionally graded CNT reinforced cylinders with various boundary conditions

  • Moradi-Dastjerdi, Rasool;Payganeh, Gholamhassan
    • Steel and Composite Structures
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    • v.24 no.3
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    • pp.359-367
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    • 2017
  • In this work, transient heat transfer analysis of functionally graded (FG) carbon nanotube reinforced nanocomposite (CNTRC) cylinders with various essential and natural boundary conditions is investigated by a mesh-free method. The cylinders are subjected to thermal flux, convection environments and constant temperature faces. The material properties of the nanocomposite are estimated by an extended micro mechanical model in volume fraction form. The distribution of carbon nanotube (CNT) has a linear variation along the radial direction of axisymmetric cylinder. In the mesh-free analysis, moving least squares shape functions are used for approximation of temperature field in the weak form of heat transform equation and the transformation method is used for the imposition of essential boundary conditions. Newmark method is applied for solution time depended problem. The effects of CNT distribution pattern and volume fraction, cylinder thickness and boundary conditions are investigated on the transient temperature field of the nanocomposite cylinders.

Buckling of sandwich plates with FG-CNT-reinforced layers resting on orthotropic elastic medium using Reddy plate theory

  • Shokravi, Maryam
    • Steel and Composite Structures
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    • v.23 no.6
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    • pp.623-631
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    • 2017
  • Present paper deals with the temperature-dependent buckling analysis of sandwich nanocomposite plates resting on elastic medium subjected to magnetic field. The lamina layers are reinforced with carbon nanotubes (CNTs) as uniform and functionally graded (FG). The elastic medium is considered as orthotropic Pasternak foundation with considering the effects of thermal loading on the spring and shear constants of medium. Mixture rule is utilized for obtaining the effective material properties of each layer. Adopting the Reddy shear deformation plate theory, the governing equations are derived based on energy method and Hamilton's principle. The buckling load of the structure is calculated with the Navier's method for the simply supported sandwich nanocomposite plates. Parametric study is conducted on the combined effects of the volume percent and distribution types of the CNTs, temperature change, elastic medium, magnetic field and geometrical parameters of the plates on the buckling load of the sandwich structure. The results show that FGX distribution of the CNTs leads to higher stiffness and consequently higher buckling load. In addition, considering the magnetic field increases the buckling load of the sandwich nanocomposite plate.

Analytical solution of buckling problem in plates reinforced by Graphene platelet based on third order shear deformation theory

  • Zhou, Linyun;Najjari, Yasaman
    • Steel and Composite Structures
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    • v.43 no.6
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    • pp.725-734
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    • 2022
  • In this paper, buckling analyses of nanocomposite plate reinforced by Graphen platelet (GPL) is studied. The Halphin-Tsai model is used for obtaining the effective material properties of nanocomposite plate. The nanocomposite plate is modeled by Third order shear deformation theory (TSDT). The elastic medium is simulated by Winkler model. Employing relations of strains-displacements and stress-strain, the energy equations of the plate are obtained and using Hamilton's principle, the governing equations are derived. The governing equations are solved based on analytical solution. The effect of GPL volume percent, geometrical parameters of plate and elastic foundation on the buckling load are investigated. Results show that with increasing GPLs volume percent, the buckling load increases. In addition, elastic medium can enhance the values of buckling load significantly.

Buckling analysis of nanocomposite cut out plate using domain decomposition method and orthogonal polynomials

  • Jamali, M.;Shojaee, T.;Kolahchi, R.;Mohammadi, B.
    • Steel and Composite Structures
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    • v.22 no.3
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    • pp.691-712
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    • 2016
  • In this editorial, buckling analytical investigation of the nanocomposite plate with square cut out reinforced by carbon nanotubes (CNTs) surrounded by Pasternak foundation is considered. The plate is presumed has square cut out in center and resting on Pasternak foundation. CNTs are used as amplifier in plate for diverse distribution, such as uniform distribution (UD) and three patterns of functionally graded (FG) distribution types of CNTs (FG-X, FG-A and FG-O). Moreover, the effective mechanical properties of nanocomposite plate are calculated from the rule of mixture. Domain decomposition method and orthogonal polynomials are applied in order to define the shape function of nanocomposite plate with square cut out. Finally, Rayleigh-Ritz energy method is used to obtain critical buckling load of system. A detailed parametric study is conducted to explicit the effects of the dimensions of plate, length of square cut out, different distribution of CNTs, elastic medium and volume fraction of CNTs. It is found from results that increase the dimensions of plate and length of square cut out have negative impact on buckling behavior of system but considering CNTs in plate has positive influence.

Transient vibration analysis of FG-MWCNT reinforced composite plate resting on foundation

  • Kumar, Puneet;Srinivas, J.
    • Steel and Composite Structures
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    • v.29 no.5
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    • pp.569-578
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    • 2018
  • This paper aims to investigate the transient vibration behavior of functionally graded carbon nanotube (FG-CNT) reinforced nanocomposite plate resting on Pasternak foundation under pulse excitation. The plate is considered to be composed of matrix material and multi-walled carbon nanotubes (MWCNTs) with distribution as per the functional grading concept. The functionally graded distribution patterns in nanocomposite plate are explained more appropriately with the layer-wise variation of carbon nanotubes weight fraction in the thickness coordinate. The layers are stacked up in such a way that it yields uniform and three other types of distribution patterns. The effective material properties of each layer in nanocomposite plate are obtained by modified Halpin-Tsai model and rule of mixtures. The governing equations of an illustrative case of simply-supported nanocomposite plate resting on the Pasternak foundation are derived from third order shear deformation theory and Navier's solution technique. A converge transient response of nanocompiste plate under uniformly distributed load with triangular pulse is obtained by varying number of layer in thickness direction. The validity and accuracy of the present model is also checked by comparing the results with those available in literature for isotropic case. Then, numerical examples are presented to highlight the effects of distribution patterns, foundation stiffness, carbon nanotube parameters and plate aspect ratio on the central deflection response. The results are extended with the consideration of proportional damping in the system and found that nanocomposite plate with distribution III have minimum settling time as compared to the other distributions.

Nonlinear vibration of FG-CNTRC curved pipes with temperature-dependent properties

  • Mingjie Liu;Shaoping Bi;Sicheng Shao;Hadi Babaei
    • Steel and Composite Structures
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    • v.46 no.4
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    • pp.553-563
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    • 2023
  • In the current research, the nonlinear free vibrations of curved pipes made of functionally graded (FG) carbon nanotube reinforced composite (CNTRC) materials are investigated. It is assumed that the FG-CNTRC curved pipe is supported on a three-parameter nonlinear elastic foundation and is subjected to a uniform temperature rise. Properties of the curved nanocomposite pipe are distributed across the radius of the pipe and are given by means of a refined rule of mixtures approach. It is also assumed that all thermomechanical properties of the nanocomposite pipe are temperature-dependent. The governing equations of the curved pipe are obtained using a higher order shear deformation theory, where the traction free boundary conditions are satisfied on the top and bottom surfaces of the pipe. The von Kármán type of geometrical non-linearity is included into the formulation to consider the large deflection in the curved nanocomposite pipe. For the case of nanocomposite curved pipes which are simply supported in flexure and axially immovable, the motion equations are solved using the two-step perturbation technique. The closed-form expressions are provided to obtain the small- and large-amplitude frequencies of FG-CNTRC curved pipes rested on a nonlinear elastic foundation in thermal environment. Numerical results are given to explore the effects of CNT distribution pattern, the CNT volume fraction, thermal environment, nonlinear foundation stiffness, and geometrical parameters on the fundamental linear and nonlinear frequencies of the curved nanocomposite pipe.

Investigation of natural solution effect in electrical conductivity of PANI-CeO2 nanocomposites

  • Shafiee, Mohammad Reza Mohammad;Sattari, Ahmad;Kargar, Mahboubeh;Ghashang, Majid
    • Steel and Composite Structures
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    • v.24 no.1
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    • pp.15-22
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    • 2017
  • A green biosynthesis method is described for the preparation of Polyaniline (PANI)-cerium dioxide ($CeO_2$) nanocomposites in different media via in-situ oxidative polymerization procedure. The effect of various media including use of HCl, Lemon Juice, Beverage, White Vinegar, Verjuice and Apple vinegar extracts on the particles size, morphology as well as the conductivity of $PANI-CeO_2$ nanocomposites was investigated. The electron-withdrawing feature of $CeO_2$ increases doping level of PANI and enhances electron delocalization. These cause a significantly blue shift of C = C stretching band of quinoid from $1570cm^{-1}$ to $1585cm^{-1}$. The optical properties of the pure material and polymeric nanocomposites as well as their interfacial interaction in nanocomposite structures analyzed by UV-visible spectroscopy. The DC electrical conductivity (${\sigma}$) of as-prepared HCl doped PANI and a $PANI-CeO_2$ nanocomposite measured by a four-probe method at room temperature was studied.

Vibrational characteristic of FG porous conical shells using Donnell's shell theory

  • Yan, Kai;Zhang, Yao;Cai, Hao;Tahouneh, Vahid
    • Steel and Composite Structures
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    • v.35 no.2
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    • pp.249-260
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    • 2020
  • The main purpose of this research work is to investigate the free vibration of conical shell structures reinforced by graphene platelets (GPLs) and the elastic properties of the nanocomposite are obtained by employing Halpin-Tsai micromechanics model. To this end, a shell model is developed based on Donnell's theory. To solve the problem, the analytical Galerkin method is employed together with beam mode shapes as weighting functions. Due to importance of boundary conditions upon mechanical behavior of nanostructures, the analysis is carried out for different boundary conditions. The effects of boundary conditions, semi vertex angle, porosity distribution and graphene platelets on the response of conical shell structures are explored. The correctness of the obtained results is checked via comparing with existing data in the literature and good agreement is eventuated. The effectiveness and the accuracy of the present approach have been demonstrated and it is shown that the Donnell's shell theory is efficient, robust and accurate in terms of nanocomposite problems.