The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
J N Reddy - One of the best experts on this subject based on the ideXlab platform.
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Fully coupled thermo-mechanical analysis of multilayered plates with embedded FGM skins or core layers using a Layerwise mixed model
Composite Structures, 2019Co-Authors: F Moleiro, V.m. Franco Correia, António J.m. Ferreira, J N ReddyAbstract:Abstract This work presents a new Layerwise mixed model for the fully coupled thermo-mechanical static analysis of multilayered plates with embedded functionally graded material (FGM) layers, either skins or core layers, under thermal and/or mechanical loads. This model is able to fully describe a two-constituent metal-ceramic FGM layer z-continuous effective properties through-thickness, using any given homogenization method, and is here extended to the fully coupled thermo-mechanical analysis. It is based on a mixed least-squares formulation with a Layerwise variable description for displacements, transverse stresses and in-plane strains, along with temperature, transverse heat flux and in-plane components of the thermal gradient, taken as independent variables. This mixed formulation ensures that the interlaminar C 0 continuity requirements, where the material properties may actually change, are fully fulfilled a priori by all chosen independent variables. The numerical results consider single-layer and multilayered plates with different side-to-thickness ratios, under thermal or mechanical loads, using mainly Mori-Tanaka estimate for the FGM effective properties with different material gradation profiles. The results are assessed by comparison with three-dimensional (3D) exact solutions, and demonstrate the model capability to predict a highly accurate quasi-3D thermo-mechanical description of the through-thickness distributions of displacements and stresses, as well as temperature and heat flux.
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Layerwise mixed models for analysis of multilayered piezoelectric composite plates using least squares formulation
Composite Structures, 2015Co-Authors: C Mota M Soares, F Moleiro, C Mota A Soares, J N ReddyAbstract:Abstract This work provides an assessment of Layerwise mixed models using least-squares formulation for the coupled electromechanical static analysis of multilayered plates. In agreement with three-dimensional (3D) exact solutions, due to compatibility and equilibrium conditions at the layers interfaces, certain mechanical and electrical variables must fulfill interlaminar C 0 continuity, namely: displacements, in-plane strains, transverse stresses, electric potential, in-plane electric field components and transverse electric displacement (if no potential is imposed between layers). Hence, two Layerwise mixed least-squares models are here investigated, with two different sets of chosen independent variables: Model A, developed earlier, fulfills a priori the interlaminar C 0 continuity of all those aforementioned variables, taken as independent variables; Model B, here newly developed, rather reduces the number of independent variables, but also fulfills a priori the interlaminar C 0 continuity of displacements, transverse stresses, electric potential and transverse electric displacement, taken as independent variables. The predictive capabilities of both models are assessed by comparison with 3D exact solutions, considering multilayered piezoelectric composite plates of different aspect ratios, under an applied transverse load or surface potential. It is shown that both models are able to predict an accurate quasi-3D description of the static electromechanical analysis of multilayered plates for all aspect ratios.
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assessment of a Layerwise mixed least squares model for analysis of multilayered piezoelectric composite plates
Computers & Structures, 2012Co-Authors: F Moleiro, C Mota M Soares, C Mota A Soares, J N ReddyAbstract:A Layerwise mixed finite element model is developed based on the least-squares formulation for the coupled electromechanical static analysis of multilayered plates with piezoelectric and composite layers. The model assumes a Layerwise variable description for displacements, transverse stresses and in-plane strains, along with the electrostatic potential, transverse electric displacement and in-plane electric field components, taken as independent variables. This original choice for the Layerwise mixed formulation is intended to ensure the a priori and complete fulfilment of the interlaminar C^0 continuity of both mechanical and electrical variables, which is due to compatibility and equilibrium conditions. Numerical applications are shown for assessment of the model predictive capabilities by comparison with available exact three-dimensional solutions, considering multilayered piezoelectric composite plates of various side-to-thickness ratios, under an applied load or surface potential.
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a Layerwise mixed least squares finite element model for static analysis of multilayered composite plates
Computers & Structures, 2011Co-Authors: F Moleiro, C Mota M Soares, C Mota A Soares, J N ReddyAbstract:A Layerwise finite element model is developed in a mixed least-squares formulation for static analysis of multilayered composite plates. The model assumes a Layerwise variable description of displacements, transverse stresses and in-plane strains, taken as independent variables. The mixed formulation allows to completely and a priori fulfil the known C"z^0 requirements, which refer to the zig-zag form of displacements in the thickness direction and the interlaminar continuity of transverse stresses, due to compatibility and equilibrium reasons, respectively. This contrasts with Layerwise displacement-based models that usually cannot a priori account for the interlaminar continuity of transverse stresses. In addition, the benefit of mixed least-squares formulation, as opposed to mixed weak form models, is that it leads to a variational unconstrained minimization problem, where the finite element approximating spaces can be chosen independently. Numerical examples are shown to assess the Layerwise mixed least-squares model predictive capabilities compared to three-dimensional elasticity solutions and also other finite element results available in literature. Most notably, the present model is able to achieve accurate results in very good agreement with three-dimensional solutions and is shown to be insensitive to shear-locking.
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Layerwise mixed least squares finite element models for static and free vibration analysis of multilayered composite plates
Composite Structures, 2010Co-Authors: F Moleiro, C Mota M Soares, C Mota A Soares, J N ReddyAbstract:Abstract Layerwise finite element models are developed based on a mixed least-squares formulation for both static and free vibration analysis of multilayered composite plates. The models assume a Layerwise variable description of displacements, transverse stresses and in-plane strains, taken as independent variables. Altogether, the benefits of this finite element formulation are twofold. First, the Layerwise mixed formulation enables the fulfilment of the so-called C z 0 requirements, completely and a priori. Specifically, the interlaminar continuity of displacements and transverse stresses, due to compatibility and equilibrium conditions, are both in the form of C0 continuous functions in the thickness z-direction. Second, the least-squares formulation leads to a variational unconstrained minimization problem, where the finite element approximating spaces can be chosen independently. Therefore, contrary to mixed weak form models, the mixed least-squares models are able to by-pass stability conditions, also known as inf-sup conditions. Ultimately, the model for static analysis yields a symmetric positive definite system of linear equations, whereas the model for free vibration analysis yields a symmetric quadratic eigenvalue problem. The numerical examples show that the models predictive capabilities are in excellent agreement with three-dimensional exact solutions, from very thick to very thin plates, and are shown to be insensitive to shear locking.
A. J. M. Ferreira - One of the best experts on this subject based on the ideXlab platform.
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analysis of composite plates using a Layerwise theory and a differential quadrature finite element method
Composite Structures, 2016Co-Authors: Bo Liu, A. J. M. Ferreira, Yufeng Xing, A. M. A. NevesAbstract:Abstract A Layerwise shear deformation theory for composite laminated plates is discretized using a differential quadrature finite element method (DQFEM). The DQFEM is a weak-form differential quadrature method that can provide highly accurate results using only a few sampling points. The Layerwise theory proposed by Ferreira is based on an expansion of Mindlin’s first-order shear deformation theory in each layer and results for a laminated plate with three layers were presented as example in the original paper. This work generalized the Layerwise theory to plates with any number of layers. The combination of the DQFEM with Ferreira’s Layerwise theory allows a very accurate prediction of the field variables. Laminated composite and sandwich plates were analyzed. The DQFEM solutions were compared with various models in literature and especially showed very good agreements with the exact solutions in literature that was based on a similar Layerwise theory. The analysis of composite plates based on Ferreira’s Layerwise theory indicates that the DQFEM is an effective method for high accuracy analysis of large-scale problems.
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A generalized Layerwise higher-order shear deformation theory for laminated composite and sandwich plates based on isogeometric analysis
Acta Mechanica, 2016Co-Authors: Chien H Thai, A. J. M. Ferreira, M. Abdel Wahab, H. Nguyen-xuanAbstract:This paper presents a generalized Layerwise higher-order shear deformation theory for laminated composite and sandwich plates. We exploit a higher-order shear deformation theory in each layer such that the continuity of the displacement and transverse shear stresses at the layer interfaces is ensured. Thanks for enforcing the continuity of the displacement and transverse shear stresses at an inner-laminar layer, the minimum number of variables is retained from the present theory in comparison with other Layerwise theories. The method requires only five variables, the same as what obtained from the first- and higher-order shear deformation theories. In comparison with the shear deformation theories based on the equivalent single layer, the present theory is capable of producing a higher accuracy for inner-laminar layer shear stresses. The free boundary conditions of transverse shear stresses at the top and bottom surfaces of the plate are fulfilled without any shear correction factors. The discrete system equations are derived from the Galerkin weak form, and the solution is obtained by isogeometric analysis (IGA). The discrete form requires the C^1 continuity of the transverse displacement, and hence NURBS basis functions in IGA naturally ensure this condition. The laminated composite and sandwich plates with various geometries, aspect ratios, stiffness ratios and boundary conditions are studied. The obtained results are compared with the 3D elasticity solution, the analytical as well as numerical solutions based on various plate theories.
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Analysis of functionally graded sandwich and laminated shells using a Layerwise theory and a differential quadrature finite element method
Composite Structures, 2016Co-Authors: Bo Liu, Y.f. Xing, A. J. M. Ferreira, A. M. A. NevesAbstract:A Layerwise shear deformation theory for functionally graded (FGM) sandwich shells and laminated composite shells is discretized using a differential quadrature finite element method (DQFEM). The DQFEM is a weak-form differential quadrature method that can provide highly accurate results using only a few sampling points. The Layerwise theory proposed by Ferreira is based on an expansion of Mindlin's first-order shear deformation theory in each layer. The combination of the DQFEM with Ferreira's Layerwise theory allows a very accurate prediction of the field variables. Effective material properties of the FGM are estimated according to both Voigt's rule of mixture (ROM) and Mori-Tanaka (MT) scheme. The DQFEM solutions were compared with various models in literature and especially showed very good agreements with results based on Layerwise theories. The analysis of FGM sandwich and laminated composite shells based on Ferreira's Layerwise theory indicates that the DQFEM is an effective method for high accuracy analysis of large-scale problems.
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analysis of sandwich plates with a new Layerwise formulation
Composites Part B-engineering, 2014Co-Authors: Dalal Adnan Maturi, A. J. M. Ferreira, Ashraf M Zenkour, Daoud S MashatAbstract:Abstract In the analysis of sandwich laminates, where core and skin materials are so different, Layerwise formulations should be adopted. In this paper the static and free vibration analysis of sandwich plates by the use of collocation with radial basis functions and using a new Layerwise theory with independent rotations in each layer and thickness stretching was performed. With this formulation, transverse normal and shear deformations and stresses are accurately computed. The equations of motion were automatically implemented via a Unified Formulation and interpolated with radial basis functions. Finally composite laminated plate and sandwich plate examples were tested and discussed.
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isogeometric analysis of laminated composite and sandwich plates using a Layerwise deformation theory
Composite Structures, 2013Co-Authors: Chien H Thai, A. J. M. Ferreira, Erasmo Carrera, H NguyenxuanAbstract:We present an isogeometric finite element formulation for static, free vibration and buckling analysis of laminated composite and sandwich plates. The idea behind this work is to associate an isogeometric analysis (IGA) with a Layerwise theory [A.J.M. Ferreira. Analyis of composite plates using a Layerwise deformation theory and multiquadrics discretization. Mech Adv Mater Struct 2005;12(2):99–112]. Isogeometric analysis based on non-uniform rational B-spline (NURBS) basic functions were recently proposed to preserve exact geometries and to enhance very significantly the accuracy of the traditional finite elements. B-splines basic function (or NURBS) is used to represent for both geometric and field variable approximations, which provide a flexible way to make refinement and degree elevation. They enable us to achieve easily the smoothness with arbitrary continuity order compared with the traditional FEM. The Layerwise theory assumes a first-order shear deformation theory in each layer and the imposition of displacement continuity at the layers interfaces. This permits to remove shear correction factors and improves the accuracy of transverse shear stresses. Intensive numerical studies have been conducted to show the highly efficient performance of the proposed formulation.
F Moleiro - One of the best experts on this subject based on the ideXlab platform.
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Fully coupled thermo-mechanical analysis of multilayered plates with embedded FGM skins or core layers using a Layerwise mixed model
Composite Structures, 2019Co-Authors: F Moleiro, V.m. Franco Correia, António J.m. Ferreira, J N ReddyAbstract:Abstract This work presents a new Layerwise mixed model for the fully coupled thermo-mechanical static analysis of multilayered plates with embedded functionally graded material (FGM) layers, either skins or core layers, under thermal and/or mechanical loads. This model is able to fully describe a two-constituent metal-ceramic FGM layer z-continuous effective properties through-thickness, using any given homogenization method, and is here extended to the fully coupled thermo-mechanical analysis. It is based on a mixed least-squares formulation with a Layerwise variable description for displacements, transverse stresses and in-plane strains, along with temperature, transverse heat flux and in-plane components of the thermal gradient, taken as independent variables. This mixed formulation ensures that the interlaminar C 0 continuity requirements, where the material properties may actually change, are fully fulfilled a priori by all chosen independent variables. The numerical results consider single-layer and multilayered plates with different side-to-thickness ratios, under thermal or mechanical loads, using mainly Mori-Tanaka estimate for the FGM effective properties with different material gradation profiles. The results are assessed by comparison with three-dimensional (3D) exact solutions, and demonstrate the model capability to predict a highly accurate quasi-3D thermo-mechanical description of the through-thickness distributions of displacements and stresses, as well as temperature and heat flux.
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Layerwise mixed models for analysis of multilayered piezoelectric composite plates using least squares formulation
Composite Structures, 2015Co-Authors: C Mota M Soares, F Moleiro, C Mota A Soares, J N ReddyAbstract:Abstract This work provides an assessment of Layerwise mixed models using least-squares formulation for the coupled electromechanical static analysis of multilayered plates. In agreement with three-dimensional (3D) exact solutions, due to compatibility and equilibrium conditions at the layers interfaces, certain mechanical and electrical variables must fulfill interlaminar C 0 continuity, namely: displacements, in-plane strains, transverse stresses, electric potential, in-plane electric field components and transverse electric displacement (if no potential is imposed between layers). Hence, two Layerwise mixed least-squares models are here investigated, with two different sets of chosen independent variables: Model A, developed earlier, fulfills a priori the interlaminar C 0 continuity of all those aforementioned variables, taken as independent variables; Model B, here newly developed, rather reduces the number of independent variables, but also fulfills a priori the interlaminar C 0 continuity of displacements, transverse stresses, electric potential and transverse electric displacement, taken as independent variables. The predictive capabilities of both models are assessed by comparison with 3D exact solutions, considering multilayered piezoelectric composite plates of different aspect ratios, under an applied transverse load or surface potential. It is shown that both models are able to predict an accurate quasi-3D description of the static electromechanical analysis of multilayered plates for all aspect ratios.
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assessment of a Layerwise mixed least squares model for analysis of multilayered piezoelectric composite plates
Computers & Structures, 2012Co-Authors: F Moleiro, C Mota M Soares, C Mota A Soares, J N ReddyAbstract:A Layerwise mixed finite element model is developed based on the least-squares formulation for the coupled electromechanical static analysis of multilayered plates with piezoelectric and composite layers. The model assumes a Layerwise variable description for displacements, transverse stresses and in-plane strains, along with the electrostatic potential, transverse electric displacement and in-plane electric field components, taken as independent variables. This original choice for the Layerwise mixed formulation is intended to ensure the a priori and complete fulfilment of the interlaminar C^0 continuity of both mechanical and electrical variables, which is due to compatibility and equilibrium conditions. Numerical applications are shown for assessment of the model predictive capabilities by comparison with available exact three-dimensional solutions, considering multilayered piezoelectric composite plates of various side-to-thickness ratios, under an applied load or surface potential.
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a Layerwise mixed least squares finite element model for static analysis of multilayered composite plates
Computers & Structures, 2011Co-Authors: F Moleiro, C Mota M Soares, C Mota A Soares, J N ReddyAbstract:A Layerwise finite element model is developed in a mixed least-squares formulation for static analysis of multilayered composite plates. The model assumes a Layerwise variable description of displacements, transverse stresses and in-plane strains, taken as independent variables. The mixed formulation allows to completely and a priori fulfil the known C"z^0 requirements, which refer to the zig-zag form of displacements in the thickness direction and the interlaminar continuity of transverse stresses, due to compatibility and equilibrium reasons, respectively. This contrasts with Layerwise displacement-based models that usually cannot a priori account for the interlaminar continuity of transverse stresses. In addition, the benefit of mixed least-squares formulation, as opposed to mixed weak form models, is that it leads to a variational unconstrained minimization problem, where the finite element approximating spaces can be chosen independently. Numerical examples are shown to assess the Layerwise mixed least-squares model predictive capabilities compared to three-dimensional elasticity solutions and also other finite element results available in literature. Most notably, the present model is able to achieve accurate results in very good agreement with three-dimensional solutions and is shown to be insensitive to shear-locking.
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Layerwise mixed least squares finite element models for static and free vibration analysis of multilayered composite plates
Composite Structures, 2010Co-Authors: F Moleiro, C Mota M Soares, C Mota A Soares, J N ReddyAbstract:Abstract Layerwise finite element models are developed based on a mixed least-squares formulation for both static and free vibration analysis of multilayered composite plates. The models assume a Layerwise variable description of displacements, transverse stresses and in-plane strains, taken as independent variables. Altogether, the benefits of this finite element formulation are twofold. First, the Layerwise mixed formulation enables the fulfilment of the so-called C z 0 requirements, completely and a priori. Specifically, the interlaminar continuity of displacements and transverse stresses, due to compatibility and equilibrium conditions, are both in the form of C0 continuous functions in the thickness z-direction. Second, the least-squares formulation leads to a variational unconstrained minimization problem, where the finite element approximating spaces can be chosen independently. Therefore, contrary to mixed weak form models, the mixed least-squares models are able to by-pass stability conditions, also known as inf-sup conditions. Ultimately, the model for static analysis yields a symmetric positive definite system of linear equations, whereas the model for free vibration analysis yields a symmetric quadratic eigenvalue problem. The numerical examples show that the models predictive capabilities are in excellent agreement with three-dimensional exact solutions, from very thick to very thin plates, and are shown to be insensitive to shear locking.
Hiroyuki Matsunaga - One of the best experts on this subject based on the ideXlab platform.
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thermal buckling of angle ply laminated composite and sandwich plates according to a global higher order deformation theory
Composite Structures, 2006Co-Authors: Hiroyuki MatsunagaAbstract:Abstract A two-dimensional global higher-order deformation theory is presented for thermal buckling of angle-ply laminated composite and sandwich plates. By using the method of power series expansion of continuous displacement components, a set of fundamental governing equations which can take into account the effects of both transverse shear and normal stresses is derived through the principle of virtual work. Several sets of truncated M th order approximate theories are applied to solve the eigenvalue problems of simply supported laminated composite and sandwich plates. In order to assure the accuracy of the present theory, convergence properties of the critical temperatures are examined in detail. Numerical results are compared with those of the published three-dimensional Layerwise theory in which both in-plane and normal displacements are assumed to be C 0 continuous in the continuity conditions at the interface between layers. Modal transverse shear and normal stresses can be calculated by integrating the three-dimensional equations of equilibrium in the thickness direction, and satisfying the continuity conditions at the interface between layers and stress boundary conditions at the external surfaces. Effects of the difference of displacement continuity conditions between the three-dimensional Layerwise theory and the global higher-order theory are clarified in thermal buckling problems of angle-ply laminated and sandwich plates.
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a comparison between 2 d single layer and 3 d Layerwise theories for computing interlaminar stresses of laminated composite and sandwich plates subjected to thermal loadings
Composite Structures, 2004Co-Authors: Hiroyuki MatsunagaAbstract:Abstract A two-dimensional global higher-order deformation theory is presented for the evaluation of interlaminar stresses and displacements in cross-ply multilayered composite and sandwich plates subjected to thermal loadings. By using the method of power series expansion of continuous displacement components, a set of fundamental governing equations which can take into account the effects of both transverse shear and normal stresses is derived through the principle of virtual work. Several sets of truncated M th order approximate theories are applied to solve the static boundary value problems of a simply supported multilayered composite plate. Transverse shear and normal stresses can be calculated by integrating the three-dimensional equations of equilibrium in the thickness direction, and satisfying the continuity conditions at the interface between layers and stress boundary conditions at the external surfaces. Numerical results are compared with those of the published three-dimensional Layerwise theory in which both in-plane and normal displacements are assumed to be C 0 continuous in the continuity conditions at the interface between layers. Effects of the difference of displacement continuity conditions between the three-dimensional Layerwise theory and the global higher-order theory are clarified in multilayered composite and sandwich plates subjected to thermal loadings.
S Pradyumna - One of the best experts on this subject based on the ideXlab platform.
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transient stress analysis of sandwich plate and shell panels with functionally graded material core under thermal shock
Journal of Thermal Stresses, 2018Co-Authors: Shashank Pandey, S PradyumnaAbstract:A finite element formulation for stress analysis of functionally graded material (FGM) sandwich plates and shell panels under thermal shock is presented in this work. A higher-order Layerwise theor...
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a finite element formulation for thermally induced vibrations of functionally graded material sandwich plates and shell panels
Composite Structures, 2017Co-Authors: Shashank Pandey, S PradyumnaAbstract:Abstract A finite element formulation based on a higher-order Layerwise theory is presented for the first time to investigate thermally induced vibrations of functionally graded material (FGM) sandwich plates and shell panels. The properties of FGM sandwich are assumed to be position and temperature dependent. The upper and lower layers of the sandwich panel are considered to be made of pure ceramic and metal, respectively and the elastic properties of FGM core are varied according to a power-law function. The top surface is exposed to a thermal shock and the bottom surface of the panel is either kept at a reference temperature or thermally insulated. The one-dimensional transient heat conduction equation is solved using a central difference scheme in conjunction with the Crank-Nicolson method. A higher-order Layerwise theory is used for FGM sandwich panels, in which a higher-order displacement field for the FGM core and a first-order displacement field for the facesheets are assumed. The governing equations are solved using Newmark average acceleration method. It is shown that the proposed Layerwise finite element formulation is simple and can easily be applied to investigate FGM sandwich plates and shell panels subjected to rapid heating.
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a new c0 higher order Layerwise finite element formulation for the analysis of laminated and sandwich plates
Composite Structures, 2015Co-Authors: Shashank Pandey, S PradyumnaAbstract:Abstract In this paper, a new Layerwise plate formulation based on a C 0 higher-order finite element model is presented for static and free vibration analyses of laminated composite and sandwich plates. The proposed Layerwise theory which is developed for a three layered composite plates, assumes higher-order displacement field for middle layer and first-order displacement field for top and bottom layers. Compatibility conditions are imposed at the layer interface to satisfy the interlaminar displacement continuity. An eight-noded isoparametric element is used to model the plate. The accuracy of the proposed formulation is assessed for linear static and free vibration analyses by comparing the authors’ results with available 3D elasticity, finite element and analytical solutions. It has been shown here that the present finite element formulation is much simpler, straightforward and accurate for static and free vibration analyses of laminated composite and sandwich plates.
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Free vibration of functionally graded sandwich plates in thermal environment using a Layerwise theory
European Journal of Mechanics A Solids, 2015Co-Authors: Shashank Pandey, S PradyumnaAbstract:In this work, a Layerwise finite element formulation is presented for the first time for dynamic analysis of two types of functionally graded material (FGM) sandwich plates with nonlinear temperature variation along the thickness and the FGM having temperature dependent material properties. Natural frequencies of sandwich plates made of FGM in thermal environment are presented using a Layerwise theory. Two configurations of sandwich plate, one with homogenous facesheets and functionally graded core and the second with functionally graded facesheets and homogenous core are considered. The material properties of both types of FGM sandwich plates are varied according to Mori-Tanaka (MT) scheme and the rule of mixture (ROM). The Layerwise theory used in this work is based on the assumption of the first order shear deformation theory in each layer and the displacement continuity is satisfied at each layer interface. In the present investigation, it is seen that the natural frequencies converge with lesser number of elements and the results are found to be accurate. Natural frequencies are presented for FGM sandwich plates with different geometric and elastic properties, thermal load and boundary conditions.
