Functionally Graded Material Sandwich Plates Research Articles

Thermal buckling analysis of a new type of rectangular FG sandwich plates using a new higher-order shear deformation theory

This article presents a novel higher-order shear deformation Theory to investigate the thermal buckling behavior of a new type of functionally graded material (FGM) sandwich structure. The study focuses on a specific configuration of rectangular FGM sandwich plate, consisting of FGM face layers and FGM core layer subjected to temperature gradients varying linearly and non-linearly across the thickness. By employing the principle of virtual work, the governing equations are derived, involving only four unknown functions. The Navier procedure is then utilized to obtain closed-form solutions. In this study, the material properties and thermal expansion coefficient of the two face layers of the sandwich plate are assumed to vary in the thickness direction according to a simple power-law distribution. In contrast, the core layer is assumed to have an exponential variation along the thickness direction. The critical thermal buckling is influenced by various factors, including the thickness, and aspect ratios of the sandwich plate, the gradient index, the type of loading, and the type of sandwich plate. The effects of these variables on the critical buckling temperature are thoroughly examined and analyzed.

Effect of bi-directional material gradation on thermo-mechanical bending response of metal-ceramic FGM sandwich plates using inverse trigonometric shear deformation theory

PurposeThe purpose of this study is to investigate the bending analysis of metal (Ti-6Al-4V)-ceramic (ZrO2) functionally graded material (FGM) sandwich plate with material property gradation along length and thickness direction under thermo-mechanical loading using inverse trigonometric shear deformation theory (ITSDT). FGM sandwich plate with a ceramic core and continuous variation of material properties has been modelled using Voigt’s micro-mechanical model following the power law distribution method. The impact of bi-directional gradation of material properties over the bending response of FGM plate under thermo-mechanical loading has been investigated in this work.Design/methodology/approachIn this study, gradation of material properties for FGM plates is considered along length and thickness directions using Voigt’s micromechanical model following the power law distribution method. This type of FGM is called bi-directional FGMs (BDFGM). Mechanical and thermal properties of BDFGM sandwich plates are considered temperature-dependent in the present study. ITSDT is a non-polynomial shear deformation theory which requires a smaller number of field variables for modelling of displacement function in comparison to poly-nominal shear deformation theories which lead to a reduction in the complexity of the problem. In the present study, ITSDT has been utilized to obtain the governing equations for thermo-mechanical bending of simply supported uni-directional FGM (UDFGM) and BDFGM sandwich plates. Analytical solution for bending analysis of rectangular UDFGM and BDFGM sandwich plates has been carried out using Hamilton’s principle.FindingsThe bending response of the BDFGM sandwich plate under thermo-mechanical loading has been analysed and discussed. The present study shows that centre deflection, normal stress and shear stress are significantly influenced by temperature-dependent material properties, bi-directional gradation exponents along length and thickness directions, geometrical parameters, sandwich plate layer thickness, etc. The present investigation also reveals that bi-directional FGM sandwich plates can be designed to obtain thermo-mechanical bending response with an appropriate selection of gradation exponents along length and thickness direction. Non-dimensional centre deflection of BDFGM sandwich plates decreases with increasing gradation exponents in length and thickness directions. However, the non-dimensional centre deflection of BDFGM sandwich plates increases with increasing temperature differences.Originality/valueFor the first time, the FGM sandwich plate with the bi-directional gradation of material properties has been considered to investigate the bending response under thermo-mechanical loading. In the literature, various polynomial shear deformation theories like first-order shear deformation theory (FSDT), third-order shear deformation theory (TSDT) and higher-order shear deformation theory (HSDT) have been utilized to obtain the governing equation for bending response under thermo-mechanical loading; however, non-polynomial shear deformation theory like ITSDT has been used for the first time to obtain the governing equation to investigate the bending response of BDFGM. The impact of bi-directional gradation and temperature-dependent material properties over centre deflection, normal stress and shear stress has been analysed and discussed.

The effect of the various porous layers on thermomechanical buckling of FGM sandwich plates

This study focuses on the thermal buckling behavior of sandwich porous plates made up of metal-ceramic functionally graded material (FGM) components using a new sinusoidal high order shear theory. The sandwich plate consists of a core plate made of either pure metal or pure ceramic, with face layers composed of a functional gradient of metal and ceramic constituents. This study examined the porosity and four porosity distribution functions in plates with FGM face layers and nonlinear temperature increase and material grading index of the face layers on the thermal buckling loads of sandwich plates.

Influences of Different Boundary Conditions and Hygro-Thermal Environment on the Free Vibration Responses of FGM Sandwich Plates Resting on Viscoelastic Foundation

This paper investigates the free vibration of functionally graded material (FGM) sandwich plates supported by different boundary conditions and influenced by a three-parameter viscoelastic foundation and hygro-thermal changes. Three types of FGM sandwich plates are studied and discussed, in which the FGM layers vary according to the power law rule and consist of ceramic and metal materials. An efficient and simple four-variable integral higher-order shear deformation theory (HSDT) is employed to model the analytical solution of the considered problem. Hamilton principle is implemented to obtain the plates’ governing equations and to derive the eigenvalue equation for the free vibration study. The model is verified by comparing numerical results with previous studies on the vibration of exponentially graded plates. New results are presented in this paper showing the influences of different boundary conditions, hygro-thermal changes, viscoelastic parameters, vibration modes, material exponents, and geometric dimensions.

Thermal Mechanical Bending Response of Symmetrical Functionally Graded Material Plates

This paper investigates the thermal mechanical bending response of symmetric functionally graded material (FGM) plates. This article proposes a thermodynamic analysis model of both the FGM plate and FGM sandwich plate, and the model only involves four control equations and four unknown variables. The control equation is based on the refined shear deformation theory and the principle of minimum potential energy. The Navier method is used to solve the control equation. According to the method, numerical examples are provided for the thermo-mechanical bending of the symmetric FGM plate and FGM sandwich plate under a simply supported boundary condition, and the accuracy of the model is verified. Finally, parameter analysis is conducted to investigate the effects of the volume fraction index, side-to-thickness ratio, thermal load, and changes in core thickness on the thermal mechanical bending behavior of the symmetric FGM plate and FGM sandwich plate in detail. It was found that the deflection of the FGM plate is greater than that of the FGM sandwich plate, while the normal stress of the FGM plate is smaller than that of the FGM sandwich plate. Moreover, the FGM plate and FGM sandwich plate are sensitive to nonlinear temperature changes.

Bending Analysis of Asymmetric Functionally Graded Material Sandwich Plates in Thermal Environments

This paper investigates the bending of asymmetric functionally graded material (FGM) sandwich plates subjected to thermo-mechanical loads in thermal environments. In this paper, a thermo-mechanical analysis model for asymmetric FGM sandwich plates is proposed, which contains only four control equations and four unknown variables. The governing equation is obtained through refined shear theory and the principle of virtual work, and the Navier method is used to solve it. Numerical examples of simply supported FGM sandwich plates under thermo-mechanical loads are given to verify the accuracy of the model. Finally, detailed studies are conducted on the bending of asymmetric FGM sandwich plates under thermo-mechanical loads, exploring the effects of various parameter changes on their bending behavior, and providing strong guidance for the application of asymmetric FGM sandwich plates in industrial production practice.

Discrete shear projection method for mechanical buckling analysis of FGM sandwich plates

This paper deals with the mechanical buckling analysis of functionally graded material (FGM) sandwich plates using quadrilateral element Q4γs based on the discrete shear projection method (DSPM) to avoid shear locking. The element has four-node and five degrees of freedom per node. It allows modelling two types of FGM sandwich plates, i.e. type A with a homogeneous core and FGM face sheets, and type B with homogeneous top and bottom layers and an FGM core. Different thickness schemes have been considered leading to symmetrical or unsymmetrical geometrical stacking. The paper focuses on the buckling in simply supported square plates under uniaxial or biaxial loads. The linear classical buckling theory (LCBT) is retained to evaluate the critical loads. The results obtained by the Q4γs element are compared with those reported by Zenkour (2005) and using another in-house finite element based on DKMQ and DKQ elements. All results are in good agreement when the LCBT is used to define critical loads, but the paper includes selected non-linear analysis based on the general-purpose finite element software ABAQUS. The results show the limit of validity of the LCBT for unsymmetrical stacking in the sandwich of type A and all sandwich of type B.

Free vibration of functionally graded sandwich plates in thermal environments

AbstractThis paper presents an analytical solution for the free vibration of functionally graded material (FGM) sandwich plates in a thermal environment. An equivalent‐single‐layer (ESL) plate theory with four variables is used to obtain the solution. Two types of sandwich plates are examined in this study: one with FGM face sheets and a homogeneous core and the other with an FGM core and homogeneous face sheets. The governing equations of motion are derived based on Hamilton's principle and then solved using the Navier method. The results of natural frequencies of simply supported FGM sandwich plates are compared with the available solutions in the literature. The effects of volume fraction distribution, geometrical parameters, and temperature increments on the free vibration characteristics are discussed in detail.

Improving the Bergan Wang Quadrilateral plate element by using the UI approach for analysis of isotropic and FGM sandwich plates

This work presents the improvement of Bergan Wang Quadrilateral (BWQ) element using the UI (unified and integrated) approach. In this approach, a new formulation of quadrilateral plate element is developed with a single independent variable just like what Bergan and Wang applied to develop a non-conforming BWQ element. The difference between the two approaches lies in the formulation of transverse displacement w, wherein the UI approach transverse displacement w is expressed as the sum of transverse bending, and shear displacements (wb and ws) and the transverse bending displacement wb becomes the single independent variable. The transverse shear displacement ws is defined as the second derivative of the transverse bending displacement wb. The rotations, curvatures, and shear strains are the first, second, and third derivatives of the bending displacement wb. The resulting non-conforming element, called UI-Q4 element, has proper rank, no shear locking problem, and passes the patch test. To examine the element convergence and accuracy, standard benchmark problems of isotropic plates, i.e. square plates, Razzaque and Morley skew plates, and circular plates, are used. The UI-Q4 element shows very good performance, which is observed by comparing it with MITC4, DSQK and BWQ elements. Moreover, the application of UI-Q4 element for analysing functionally graded material (FGM) sandwich plate analysis also performs well and delivers results which are quickly converged to the reference values.

Porosity-dependent buckling analysis of elastically supported FGM sandwich plate via new tangent HSDT: A meshfree approach

In this paper, new tangent shape function-based higher-order transverse shear deformation theory (NTHSDT) is proposed to compute the buckling behavior of the elastically supported functionally graded material (FGM) sandwich plates under porous medium. The proposed theory is found to be variationally consistent and fulfills the zero traction boundary conditions on the bottom and top layer without a shear correction factor. The material properties are presumed to be graded in the thickness direction as characterized by a modified power law distribution in terms of volume fraction of constituents. The governing equations are derived using Hamilton’s Principle. A strong form of solution discretizes the governing equations by employing a thin plate spline radial basis function-based collocation (TSRBFC) method. The proposed theory is efficient, reliable, and is in close agreement with the results in the literature. Comparison studies show that the NTHSDT is more accurate than other plate theories and is simple in analyzing buckling behavior. A parametric study is done to examine the effects of grading index, porosity index, sandwich schemes, aspect ratio, side-to-length thickness ratio and foundation stiffness.

A Unified Transient Vibration Analysis of FGM Sandwich Plates in Thermal Environment Based on a Further Refined Zigzag Plate Theory

In this study, a simple and unified process is established for transient vibration analysis of functionally graded material (FGM) sandwich plates in thermal environment. The temperature field, considered constant in the plane, is distributed along the thickness with uniform, linear and nonlinear profiles. For the material properties, both temperature and position dependence are taken into account. A further refined zigzag plate theory accounting for partitioned transverse displacements and piecewise-continuous in-plane displacements is developed within the framework of Hamilton’s principle including thermal effects. Appropriately and simplicity representation of the deformation states is provided in the governing equations. A spectral analysis technique, namely, method of reverberation ray matrix (MRRM), is employed to calculate the transient vibration responses of FGM sandwich plates with general boundary conditions and arbitrary external loadings. The artificial spring technology and the equivalent wave source vector are introduced to improve the numerical stability and parametric adjustability of MRRM. The accuracy, flexibility and efficiency of the proposed process are discussed using many numerical examples. On this basis, the effects of the boundary parameters, FGM gradient index, core-to-facesheet thickness ratio, thermal properties and external loadings on the transient vibration behaviors of FGM sandwich plates are thoroughly investigated.

Vibration and stability characteristics of functionally graded sandwich plates with/without porosity subjected to localized edge loadings

This article investigates the influence of porosity and localized edge loads on the vibration and buckling characteristics of functionally graded material (FGM) plates using the finite element (FE) method. The analysis is carried out by choosing a single-layer FGM and two different types of FGM sandwich plates in such a way that there is no material discontinuity along the thickness direction. The porosity imperfections are accounted for in this study as criteria of stiffness reduction and are incorporated using modified power law distribution. The vibration and buckling responses are studied by considering four types of localized edge loads on plates with different porosity distributions. The application of different types of localized edge loads on the plate leads to the development of nonuniform in-plane stresses. Hence, they are computed first by using a dynamic approach before obtaining the buckling loads. The accuracy of the FE formulation is first validated for FGM plates by comparing the natural frequencies and the critical buckling loads obtained in the present investigation with the solutions already available in the literature. After validating the accuracy, detailed parametric studies have been performed on plates with varying volume fraction exponent, porosity distribution, porosity index, side-to-thickness ratio, load width ratio, aspect ratio, and support condition, and the results are presented with appropriate conclusions. A probabilistic sensitivity analysis is carried out to identify the significant parameter affecting the buckling load and natural frequency of porous FGM plates subjected to localized edge loads, which considerably aids in the design of the FGM plates.

Effect of Porosity on the Thermal Buckling Analysis of Power and Sigmoid Law Functionally Graded Material Sandwich Plates Based on Sinusoidal Shear Deformation Theory

This work examines the effect of porosity distributions on thermal buckling analysis of functionally graded material (FGM) sandwich plates. To consider the porosity effect, five different types of distribution models, even, uneven, logarithmic uneven, linear uneven, and sinusoidal uneven are considered. It is assumed that the FGM faces of the sandwich plate are porous while the ceramic core is nonporous. To investigate the thermal buckling behavior of porous FGM sandwich plates, four different types of thermal loads, such as uniform, linear, nonlinear, and sinusoidal temperature rise along the thickness direction are considered. Effective material properties and thermal expansion coefficients of FGM sandwich plates are evaluated based on Voigt’s micromechanical model considering power law FGM (P-FGM) and sigmoid function FGM (S-FGM). The analytical solution is carried out using Hamilton’s variational principle considering the von Karman nonlinearity. The equilibrium and stability equations are derived based on sinusoidal shear deformation theory (SSDT). Numerical results are obtained to observe the influence of different porosity distributions, porosity coefficients, thermal loadings, and geometrical parameters over critical thermal buckling temperature.

Influence of geometric imperfections on the free vibrational response of the functionally graded material sandwich plates with circular cut-outs

The influence of circular cut-outs and geometric imperfection on the free vibration analysis of functionally graded material (FGM) sandwich plates with (2-1-2) plate configuration conditions has been investigated in this paper. Geometric imperfections, such as sine-type and global-type imperfections, are especially susceptible to plate vibration analysis, and these imperfections can be considered while studying plate vibration behavior. The governing equations are formulated based on the Lagrangian principle for the vibration analysis of the FGM sandwich plates subjected to the simply-supported and clamped boundary conditions. The results have been obtained using a C0-continuity isoparametric formulation with four noded elements having seven degrees of freedom per node. The accuracy of the present results has been confirmed by comparing the present results with the reported literature.

Effect of porosity and skew edges on transient response of functionally graded sandwich plates

This work for the first time presents the effect of porosity and skew edges on the transient response of functionally graded material (FGM) sandwich plates using a layerwise finite element formulation. Two configurations of FGM sandwich plates are considered. In the first configuration, the top and the bottom layers are made of the FGM and the core is made of pure metal, whereas in the second configuration, the bottom, core and the top layers are made of pure metal, FGM and pure ceramic, respectively. Four micromechanics models based on the rule of mixture are used to model porosity for these two configurations of FGM sandwich plates. A layerwise theory based on a first-order shear deformation theory for each layer that maintains the displacement continuity at the layer interface is used for the present investigation. An eight-noded isoparametric element with nine degrees of freedom per node is used to develop the finite element model (FEM). The governing equations for the present investigation are derived using Hamilton’s principle. A wide range of comparison studies are presented to establish the accuracy of the present FEM formulation. It has been shown here that the parameters like skew angle, porosity coefficient, volume fraction index, core to facesheet thickness ratio and boundary conditions have a significant effect on the transient response of FGM sandwich plates. Also, the present finite element formulation is simple and accurate.

Buckling Analysis of Functionally Graded Sandwich Plates under Both Mechanical and Thermal Loads.

This paper presents an analytical solution for the thermomechanical buckling of functionally graded material (FGM) sandwich plates. The solution is obtained using a four-variable equivalent-single-layer (ESL) plate theory. Two types of sandwich plates are included: one with FGM facesheets and homogeneous core, and vice versa for the other. The governing equations are derived based on the principle of minimum total potential energy. For simply supported boundary conditions, these equations are solved via the Navier method. The results on critical buckling load and temperature increment of simply supported FGM sandwich plates are compared with the available solutions in the literature. Several results are presented considering various material and geometrical parameters as well as their effect on the thermomechanical buckling response of FGM sandwich plates. The relationship between the mechanical load and the temperature increment for uniform/linear temperature rise of FGM sandwich plates under combined mechanical and thermal loads is studied.

Free vibration and transient dynamic response of functionally graded sandwich plates with power-law nonhomogeneity by the scaled boundary finite element method

Functionally graded materials have widespread applications for the practical engineering and industry of design and development. In the present work, free vibration and transient dynamic behaviors of functionally graded material (FGM) sandwich plates are semi-analytically investigated by the scaled boundary finite element method (SBFEM). A layerwise approach based on the three-dimensional (3D) theory of elasticity is adopted for the simulation of FGM sandwich plates, and the material properties involving Young’s modulus and mass density are assumed to be continuously graded in the thickness direction according to a power law function while Poisson’s ratio is taken to be constant in each individual layer. In order to obtain the global equilibrium equations for the dynamic problem of FGM sandwich plates, the SBFEM governing equation associated with a single layer is derived based on the principle of virtual work in the first step. Subsequently, they are assembled for the whole FGM sandwich plate by imposing the continuity conditions of the layer interface in the displacement fields. Natural frequencies are determined by eigenvalue analysis, and the transient dynamic equilibrium equation is solved on the basis of the Newmark’s method. One of the advantages of present technique is the capability of reducing the spatial dimension and no discretizations in the thickness direction are needed, which results in a considerable reduction in the computational costs of the project. Furthermore, dynamic responses can be obtained directly from the semi-analytical solutions without shear correction factors or special treatments for the shear-locking effect as some high-order shear deformation plate theories. Excellent adaptability in mesh distortion, thickness ratio and boundary condition of proposed formulations for the dynamic analysis of FGM sandwich plates are confirmed and comprehensive parametric investigations are also carried out. Numerical results show that the dynamic responses obtained by the proposed approach converge rapidly and excellent agreement can be achieved between SBFEM results and the available solutions with a small number of computational costs, which indicates high accuracy and efficiency of the proposed formulations in dynamic analyses of FGM sandwich plates.

Buckling analysis of three-dimensional functionally graded sandwich plates using two-dimensional scaled boundary finite element method

For the stability analysis of functionally graded material (FGM) sandwich plates, a semi-analytical scaled boundary finite element method (SBFEM) is established within the frame work of layerwise theory in this paper. Two different configurations of FGM sandwich plates are studied, one of which consists of ceramic-rich core and FGM face sheets, and another involves metal-rich and ceramic-rich material face sheets as well as a FGM core, and the modulus of elasticity for each FGM layer is assumed to be changed continuously along thickness according to a power-law distribution. The layerwise theory performed in present work is based on the three-dimensional theory of elasticity for each individual layer satisfying the displacement continuity boundary conditions at layer interfaces, and the two-dimensional high order spectral element with three degrees of freedom per node is employed to discrete the reference surface of each individual layer. And then, based on the principle of virtual work, the SBFEM governing equation for each individual layer of FGM sandwich plates is derived, and a dual variable including the displacement and internal nodal force is used to reduce the governing equations to a system of first-order ordinary differential equation, which is solved analytically by a general approach. Finally, the critical buckling load can be obtained by solving the eigenvalue equation once the bending stiffness matrix and geometric stiffness matrix of FGM sandwich plates are determined. Fast rate of convergence of the proposed formulations is confirmed and comparison studies are presented to construct its high accuracy and excellent predictive capability. Furthermore, effects of gradient index, side-to-thickness ratio, layer configuration, and boundary conditions on dimensionless critical buckling loads of FGM sandwich plates are also studied. The proposed semi-analytical approach is simple in program implementation, accurate and computationally efficient.

Analysis of vibration and sound insulation characteristics of functionally graded sandwich plates

Based on the first-order shear deformation theory, free vibration and sound insulation of functionally graded material (FGM) sandwich plates with four simply supported edges are studied and analyzed. The sandwich plate with FGM face sheets and homogeneous core and the sandwich plate with FGM core and homogeneous face sheets are considered. Using Navier method and fluid–solid coupling conditions, the vibration and coupled vibro-acoustic dynamic equations for FGM sandwich plates with simply supported edges are established and solved numerically. The natural frequencies and the sound insulation of FGM sandwich plates obtained theoretically are compared with the numerical simulation results. It is shown that the theoretical model of the vibration and the coupling vibro-acoustic theoretical model for the FGM sandwich plate are accurate and feasible. On this basis, the sound insulation characteristics of two types of FGM sandwich plates are analyzed, and the effects of parameter changes (incident angles, gradient index, core thickness, Poisson's ratio) on the fundamental frequency and sound insulation are discussed.

A quasi-3D trigonometric shear deformation theory for wave propagation analysis of FGM sandwich plates with porosities resting on viscoelastic foundation

In the present work, a quasi three-dimensional trigonometric shear deformation plate theory (quasi-3D TSDPT) is proposed for the wave propagation analysis of porous functionally graded material (FGM) sandwich plates resting on a viscoelastic foundation. The present plate theory accounts for the transverse shear and normal deformations by dividing the transverse displacement into bending, shear, and stretching components. Different types of FGM sandwich plates are taken into account. The porosities in the FGM layers of the sandwich structures are described by introducing the porosity volume fraction and the step function. The equations of motion governing the wave propagation behavior of porous FGM sandwich plates are derived by employing Hamilton’s principle. The analytical solutions to the wave dispersion relations are presented. Additionally, the parametric research is conducted to highlight the effects of the wave number, the porosity volume fraction, the viscoelastic foundation, the power-law exponent and the core-to-thickness ratio on the wave propagation. Results manifest that the influences of these parameters are significant on the wave propagation characteristics of porous FGM sandwich plates.