• Advances in nano research
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• v.12 no.6
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• pp.593-603
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• 2022

The critical buckling temperature rise of a newly proposed piezoelectrically active sandwich plate (ASP) has been investigated in this work. This structure includes a porous polymeric layer integrated between two piezoelectric nanocomposite layers. The piezoelectric material is made of a passive polymeric material that is activated by lead-free nanowires (NWs) of zinc oxide (ZnO) embedded inside the matrix. In both nanocomposite layers and porous core, functional graded (FG) patterns have been considered for the distributions of ZnO NWs and voids, respectively. By adopting a higher-order theory of plates, the governing equations of thermal buckling are obtained. This set of equations is then treated using an extended mesh-free solution. The effects of plate dimensions, porosity states, and the nanowire parameters have been investigated on the critical buckling temperature rises of the proposed lightweight ASPs with different boundary conditions. The results disclose that the use of porosities in the core and/or mixing ZnO NWs in the face sheets substantially arise the critical buckling temperatures of the newly proposed active sandwich plates.

• Advances in aircraft and spacecraft science
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• v.10 no.1
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• pp.83-106
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• 2023

In this work, the static behavior of FGM macro and nano-plates under thermomechanical loading. Equilibrium equations are determined by using virtual work principle and local and non-local theory. The novelty of the current model is using a new displacement field with four variables and a warping function considering the effect of shear. Through this analysis, the considered sandwich FGM macro and nanoplates are a homogeneous core and P-FGM faces, homogeneous faces and an E-FGM core and finally P-FGM faces and an E-FGM core. The analytical solution is obtained by using Navier method. The model is verified with previous published works by other models and very close results are obtained within maximum 1% deviation. The numerical results are performed to present the influence of the various parameters such as, geometric ratios, material index as well as the scale parameters are investigated. The present model can be applicable for sandwich FG plates used in nuclear, aero-space, marine, civil and mechanical applications.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.15 no.1
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• pp.39-48
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• 2006

In this paper, polymer composites based sandwich structures like beams and plates are optimised by using parametric study. The structures are composed of fibre reinforced composites for facial material and resin concrete and PVC foam for core materials. The stacking sequences and thickness of the composites are controlled as major parameters to find out the optimal condition for machine tool components. For the plate structure of machine tool bed composites-skined sandwich structure which has several ribs are proposed to enhance bending stiffnesses in two major directions at the same time. Dynamic robustness of a machine tool structure is investigated using modal analysis. From the results optimal configuration and materials for high precesion machine tools are proposed. And the plate was made of fiber reforced composite material and PVC foam.

• Steel and Composite Structures
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• v.25 no.4
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• pp.389-401
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• 2017

In this work, a new higher shear deformation theory (HSDT) is developed for the free vibration and buckling of functionally graded (FG) sandwich plates. The proposed theory presents a new displacement field by using undetermined integral terms. Only four unknowns are employed in this theory, which is less than the classical first shear deformation theory (FSDT) and others HSDTs. Equations of motion are obtained via Hamilton's principle. The analytical solutions of FG sandwich plates are determined by employing the Navier method. A good agreement between the computed results and the available solutions of existing HSDTs is found to prove the accuracy of the developed theory.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.05a
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• pp.320-323
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• 2008

In this study, a macroscopic approach was carried out to gain insight into the bending mechanism of metallic sandwich plates. Shear force-punch stroke curves for various clearances were analytically derived for mild steel (CSP 1N) sandwich plates with the total thickness of 3 mm and 0.5 mm face sheets. As the clearance increases, shear force of the inner structures and sensitivity of punch stroke decrease. These data are useful to derive a criterion of judgment for core shear failure and de-bonding failure during U-bending.

• Journal of the Society of Naval Architects of Korea
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• v.46 no.2
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• pp.155-164
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• 2009

In this paper, a spectral finite element method for a rectangular sandwich plate with viscoelastic core having the Levy-type boundary conditions has been plated. The sandwich plate consists of two isotropic and elastic face plates with a surfaced-bonded viscoelastic core. For the analysis, the in-plane and transverse energy in the face plates and only shear energy in the core are considered, respectively. To account for the frequency dependent complex shear modulus of the viscoelastic core, the Golla-Hughes-McTavish model is adopted. To evaluate the validity and accuracy of the proposed method, the frequency response function and dynamic responses of the sandwich plate with all edges simply supported subject to an impact load are calculated and compared with those calculated by a finite element method. Though these calculations, it is confirmed that the proposed method is very reliable and efficient one for vibration analysis of a rectangular sandwich plate with viscoelastic core having the Levy-type boundary conditions.

• Steel and Composite Structures
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• v.44 no.1
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• pp.65-79
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• 2022

The main goal of this paper is to study the vibration of damaged core laminated annular plates with FG face sheets based on a three-dimensional theory of elasticity. The structures are made of a damaged isotropic core and two external face sheets. These skins are strengthened at the nanoscale level by randomly oriented Carbon nanotubes (CNTs) and are reinforced at the microscale stage by oriented straight fibers. These reinforcing phases are included in a polymer matrix and a three-phase approach based on the Eshelby-Mori-Tanaka scheme and on the Halpin-Tsai approach, which is developed to compute the overall mechanical properties of the composite material. In this study the effect of microcracks on the vibrational characteristic of the sandwich plate is considered. In particular, the structures are made by an isotropic core that undergoes a progressive uniform damage, which is modeled as a decay of the mechanical properties expressed in terms of engineering constants. These defects are uniformly distributed and affect the central layer of the plates independently from the direction, this phenomenon is known as "isotropic damage" and it is fully described by a scalar parameter. Three complicated equations of motion for the sectorial plates under consideration are semi-analytically solved by using 2-D differential quadrature method. Using the 2-D differential quadrature method in the r- and z-directions, allows one to deal with sandwich annular plate with arbitrary thickness distribution of material properties and also to implement the effects of different boundary conditions of the structure efficiently and in an exact manner. The fast rate of convergence and accuracy of the method are investigated through the different solved examples. The sandwich annular plate is assumed to have any arbitrary boundary conditions at the circular edges including simply supported, clamped and, free. Several parametric analyses are carried out to investigate the mechanical behavior of these multi-layered structures depending on the damage features, through-the-thickness distribution, and boundary conditions.

• Computers and Concrete
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• v.32 no.1
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• pp.61-74
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• 2023

This article investigates the wave propagation analysis of the imperfect functionally graded (FG) sandwich plates based on a novel simple four-variable integral quasi-3D higher-order shear deformation theory (HSDT). The thickness stretching effect is considered in the transverse displacement component. The presented formulation ensures a parabolic variation of the transverse shear stresses with zero-stresses at the top and the bottom surfaces without requiring any shear correction factors. The studied sandwich plates can be used in several sectors as areas of aircraft, construction, naval/marine, aerospace and wind energy systems, the sandwich structure is composed from three layers (two FG face sheets and isotropic core). The material properties in the FG faces sheet are computed according to a modified power law function with considering the porosity which may appear during the manufacturing process in the form of micro-voids in the layer body. The Hamilton principle is utilized to determine the four governing differential equations for wave propagation in FG plates which is reduced in terms of computation time and cost compared to the other conventional quasi-3D models. An eigenvalue equation is formulated for the analytical solution using a generalized displacements' solution form for wave propagation. The effects of porosity, temperature, moisture concentration, core thickness, and the material exponent on the plates' dispersion relations are examined by considering the thickness stretching influence.

• International Journal of Aerospace System Engineering
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• v.3 no.1
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• pp.10-16
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• 2016

A trigonometric Layerwise higher order shear deformation theory (TLHSDT) is developed and implemented for free vibration and buckling analysis of laminated composite and sandwich plates by analytical and finite element formulation. The present model assumes parabolic variation of out-plane stresses through the depth of the plate and also accomplish the zero transverse shear stresses over the surface of the plate. Thus a need of shear correction factor is obviated. The present zigzag model able to meet the transverse shear stress continuity and zigzag form of in-plane displacement continuity at the plate interfaces. Hence, botheration of shear correction coefficient is neglected. In the case of analytical method, the governing differential equation and boundary conditions are obtained from the principle of virtual work. For the finite element formulation, an efficient eight noded $C^0$ continuous isoparametric serendipity element is established and employed to examine the dynamic analysis. Like FSDT, the considered mathematical model possesses similar number of variables and which decides the present models computationally more effective. Several numerical predictions are carried out and results are compared with those of other existing numerical approaches.

• Smart Structures and Systems
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• v.18 no.2
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• pp.267-291
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• 2016

In this research work, an exact analytical solution for thermal buckling analysis of functionally graded material (FGM) sandwich plates with clamped boundary condition subjected to uniform, linear, and non-linear temperature rises across the thickness direction is developed. Unlike any other theory, the number of unknown functions involved is only four, as against five in case of other shear deformation theories. The theory accounts for parabolic distribution of the transverse shear strains, and satisfies the zero traction boundary conditions on the surfaces of the plate without using shear correction factor. A power law distribution is used to describe the variation of volume fraction of material compositions. Equilibrium and stability equations are derived based on the present refined theory. The non-linear governing equations are solved for plates subjected to simply supported and clamped boundary conditions. The thermal loads are assumed to be uniform, linear and non-linear distribution through-the-thickness. The effects of aspect and thickness ratios, gradient index, on the critical buckling are all discussed.