Sandwich Cylindrical Panels Research Articles

Free vibration analysis of micro-magneto-electro-elastic cylindrical sandwich panel considering functionally graded carbon nanotube–reinforced nanocomposite face sheets, various circuit boundary conditions, and temperature-dependent material properties using high-order sandwich panel theory and modified strain gradient theory

In this article, based on high-order sandwich panel theory and modified strain gradient theory, free vibration analysis of a micro-magneto-electro-elastic sandwich panel with a transversely flexible core and functionally graded carbon nanotube–reinforced nanocomposite face sheets is investigated. Also, the influences of temperature-dependent material properties and various circuit boundary conditions such as open and closed are considered in this study. Carbon nanotubes are arranged in longitudinal direction inside polyvinylidene fluoride matrix with various functionally graded (FG) distributions such as uniform, FG-V, FG-A, FG-X, and FG-O in the face sheets. The generalized rule of mixture is employed to predict mechanical, electrical, magnetic, and thermal properties of micro-sandwich composite panel. The classical shell theory and an elasticity high-order theory are used for the face sheets and the core, respectively. Then, the governing equations of motion are derived using Hamilton’s principle. In this article, the influences of the volume fraction, the various distributions of carbon nanotubes, the multi-physical fields, open- and closed-circuit boundary conditions, the material length scale parameters, different face sheet and core thicknesses, and temperature changes on the natural frequency are investigated, and the obtained results show that these influences play an important role in the natural frequencies and can be used in order to prevent the resonance phenomenon and also for manufacturing process design and optimization of micro-magneto-electro-elastic composite sandwich cylindrical panels.

Comment on ‘Free vibration and buckling analyses of cylindrical sandwich panel with magneto rheological fluid layer’ (Journal of Sandwich Structures and Materials, doi: 10.1177/1099636215603034)

Comment on ‘Free vibration and buckling analyses of cylindrical sandwich panel with magneto rheological fluid layer’ (Journal of Sandwich Structures and Materials, doi: 10.1177/1099636215603034)

Experimental Investigations of Compressed Sandwich Composite/Honeycomb Cylindrical Shells

This article explains in some details the behaviour of thick, deep cylindrical sandwich panels subjected to compressive loads. In general, experimental results indicated that two different forms of failure have been observed – the first corresponds to the overall buckling and the second to the facesheet wrinkling. The obtained experimentally damages of shells are verified and validated with the use of the FE analysis, 2-D and 3-D both in the linear and non-linear approach. The unidirectional strain gauges were applied to detect the initiation of the overall buckling mode.

Influence of manufacturing defects on modal properties of composite pyramidal truss-like core sandwich cylindrical panels

Defects can easily appear in composite lattice truss core sandwich structures during the complex preparation process, which may significantly affect the structural response and decrease the load-carrying capability. The purpose of this paper is to investigate the manufacturing defect sensitivity of modal vibration responses of carbon fiber composite pyramidal truss-like core sandwich cylindrical panels by modal experiments and finite element analysis. Defects including debonding between face sheets and truss cores (DFT), truss missing (DTM), face sheet wrinkling (DFW) and gap reinforcing (DGR) are introduced into the present intact specimen artificially and modal testing is conducted to study their dynamic behavior under free-free boundary conditions. Finite element models consistent with the experiments are then developed to further study the effect of defect extents, locations and forms on the modal parameters of the present sandwich cylindrical panels. Results indicate that the degree of sensitivity of natural frequencies of the present sandwich cylindrical panels mainly depends on the vibration modes, defect extents, locations and forms. In addition, damping loss factors are much more sensitive than their corresponding frequencies. Some conclusions and essential mechanisms are summarized, which is helpful to vibration-based non-destructive evaluation (NDE) of such kind of composite lattice sandwich structures.

A general exact elastic shell solution for bending analysis of functionally graded structures

This new work proposes a three-dimensional (3D) exact shell model for the static analysis of simply-supported structures embedding Functionally Graded Material (FGM) layers when they are subjected to harmonic transverse normal loads. Results are proposed in terms of displacement and stress amplitudes through the thickness direction. One-layered FGM plates and cylinders, and sandwich cylindrical and spherical shell panels embedding an internal FGM core and external classical skins have been analyzed. Proposed results give a complete 3D description of FGM structures in terms of displacement and stress states. Such results can be used to validate new refined 2D shell models proposed in numerical or analytical form. Different geometries, lamination schemes, thickness ratios, materials and FGM laws through the thickness have been analyzed in order to have a general overview of the problem. The proposed 3D shell model uses the spherical 3D equilibrium equations developed in general orthogonal curvilinear coordinates. These equations automatically degenerate in those for cylindrical and plate structures via opportune considerations made about the radii of curvature. Equilibrium equations are solved in closed form considering simply supported boundary conditions and harmonic applied loads. The exponential matrix method has been employed to solve the second order partial differential equations in z. These equations have constant coefficients because of the introduction of opportune mathematical layers for the FGM description and for the curvature evaluation. A layer-wise approach has been identified with the direct imposition in the 3D shell model of equilibrium conditions for transverse stresses and compatibility conditions for displacements.

Vibration Analysis of a Cylindrical Sandwich Panel with Flexible Core Using an Improved Higher-Order Theory

This paper deals with free vibration analysis of thick cylindrical composite sandwich panels with simply supported boundary conditions based on a new improved higher-order sandwich panel theory. The formulation used the third-order polynomial description for the displacement fields of thick composite face sheets and for the displacement fields in the core layer based on the displacement field of Frostig's second model. In this case, the unknowns were coefficients of the polynomials in addition to displacements of the top and bottom face sheets. The fully dynamic effects of the core layer and face sheets were also considered in this study. Using Hamilton's principle, the governing equations were derived. Moreover, the effect of some important parameters such as those of thickness ratio of the core to panel, the length to radius ratio of the core and composite lay-up sequences were investigated on free vibration response of the panel. The results were validated by those published in the literature and with the finite element results obtained by ABAQUS. It was shown that thicker panels with thicker cores provided greater resistance to resonant vibrations. Moreover, the effect of increasing face sheets’ thicknesses in general was the significant increase in fundamental natural frequency values.

Nonlinear two-dimensional finite element model for transient and damping analysis of cylindrical sandwich panels with pseudoelastic shape memory alloy composite face sheets

A new nonlinear finite element model is proposed for the dynamic analysis of cylindrical sandwich panels with shape memory alloy hybrid composite face sheets and flexible core. In order to present a realistic transient vibration analysis, all the material complexities arising from the instantaneous and spatial martensite phase transformation of the shape memory alloy wires are taken into consideration. The one-dimensional constitutive equation proposed by Boyd and Lagoudas is used for modeling the pseudoelastic behavior of the shape memory alloy wires. Since the martensite volume fraction at each point depends on the stress at that point, the phase transformation kinetic equations and the governing equations are coupled together. Therefore, at each time step, an iterative method should be used to solve the highly nonlinear equations. Moreover, considering that the stress resultants generated by the martensite phase transformation in the wires are path-dependent values, an incremental method is used to estimate the increment of the stress resultants at each time step. The governing equations are derived based on the energy method and Newmark time integration method is used to solve the discretized finite element equations. Finally, several numerical examples are presented to examine the effect of various parameters such as intensity of applied pressure load, operating temperature, location of shape memory alloy wires, volume fraction of the shape memory alloy wires, and also boundary conditions upon the loss factor for panels with different aspect ratios.

Elastic-plastic behavior of sandwich cylindrical shell panels with a flexible core

The linear static elastic-plastic behavior of sandwich cylindrical shell panels under a generally distributed loading with thick flexible core is studied. The core modeling is based on high-order theory of sandwich structures in which the in-plane stresses of the core are neglected. The faces are modeled based on Kirchhoff–Love shell theory. The materials of the faces and the core are assumed to be isotropic with linear work hardening behavior. The incremental Prandtl–Reuss plastic flow theory is used in this analysis. Using the principle of virtual displacements, the governing equations are derived and solved for any sort of boundary conditions based on elastic-plastic harmonic differential quadrature method. To validate the results of present study, various responses in different sandwich shell panel configurations are compared with the results from finite element software Ansys. The effect of core flexibility and its plastic properties as well as the initiation of yield in faces and the core are studied in detail.

An approach in deformation and stress analysis of elasto-plastic sandwich cylindrical shell panels based on harmonic differential quadrature method

Using harmonic differential quadrature method, an approach to analyze sandwich cylindrical shell panels with any sort of boundary conditions under a generally distributed static loading, undergoing elasto-plastic deformation is proposed. The faces of the sandwich shell panel are made of some isotropic materials with linear work hardening behavior while the core is assumed to be an isotropic material experiencing only elastic behavior. The faces are modeled as thin cylindrical shells obeying the Kirchhoff–Love assumptions. For the core material, it is assumed to be thick and the in-plane stresses are negligible. Upon application of an inner and outer general lateral loading, the governing equations are derived using the principle of virtual displacements. Using an iterative approach, named elasto-plastic harmonic differential quadrature method (EP-HDQM), the equations are solved. The obtained results are compared with the results from finite element software Ansys for different sandwich shell panel configurations. Then, the effects of changing different parameters on the stress and displacement components of sandwich cylindrical shell panels in different elasto-plastic conditions are investigated.

Buckling optimisation of sandwich cylindrical panels

AbstractIn this paper, the buckling load optimisation is performed on sandwich cylindrical panels. A finite element program is developed in MATLAB to solve the governing differential equations of the global buckling of the structure. In order to find the optimal solution, the genetic algorithm Toolbox in MATLAB is implemented. Verifications are made for both the buckling finite element code and also the results from the genetic algorithm by comparisons to the results available in literature. Sandwich cylindrical panels are optimised for the buckling strength with isotropic or orthotropic cores with different boundary conditions. Results are presented in terms of stacking sequence of fibers in the face sheets and core to face sheet thickness ratio.

Free vibration and buckling analyses of cylindrical sandwich panel with magneto rheological fluid layer

In this paper, the free vibration and buckling analyses of the cylindrical sandwich panel with magneto-rheological fluid layer for simply supported boundary conditions was performed based on an improved higher order sandwich panel theory. This paper deals with investigation of the effects of magnetic field, geometrical parameters such as the core thickness to the panel thickness ratio, MR layer thickness to the panel thickness ratio and the fiber angle on the natural frequencies, loss factors and buckling loads corresponding to the first four mode shapes. In order to validate the results obtained from the present study, the cylindrical sandwich panel was simulated and analyzed in finite element software ABAQUS. A good agreement was observed between the results of present method and those extracted from simulation.

Free vibration analysis of cylindrical and rectangular sandwich panels with a functionally graded core

Based on the Reissner assumptions, the free vibration analysis of simply supported cylindrical and rectangular sandwich panels with isotropic face sheets and a functionally graded core is concerned. Firstly, the expressions of the displacements, stresses and internal forces are presented according to the constitutive relations and stress states of the core and face sheets. Then, the dynamic stability and compatibility equations are given for cylindrical sandwich panels with functionally graded core, elastic modulus and density in which vary continuously in the thickness direction. Finally, the proposed solutions are validated by comparing the results of degenerate example with classical solutions, and a numerical analysis is performed on the example of simply supported cylindrical and rectangular sandwich panels. The elastic modulus and density of the functionally graded core are assumed to be graded by a power law distribution of volume fractions of the constituents, and the Poisson ratio is held constant. The effects of the distribution of functionally graded core’s properties, the thickness-side ratios and ratio of radius (R) to length (l) κ = R/l are also examined.

High Order Impact Elastic Analysis of Circular Thick Cylindrical Sandwich Panels Subjected to Multi-mass Impacts

THIS STUDY DEALT WITH THE DYNAMIC MODEL OF COMPOSITE CYLINDRICAL SANDWICH PANELS WITH FLEXIBLE CORES AND SIMPLY SUPPORTED BOUNDARY CONDITIONS UNDER LOW VELOCITY IMPACTS OF MULTIPLE LARGE OR SMALL MASSES USING A NEW IMPROVED HIGHER ORDER SANDWICH PANEL THEORY (IHSAPT). IN-PLANE STRESSES WERE CONSIDERED FOR THE CORE AND FACE SHEETS. FORMULATION WAS BASED ON THE FIRST ORDER SHEAR DEFORMATION THEORY FOR THE COMPOSITE FACE SHEETS AND POLYNOMIAL DESCRIPTION OF THE DISPLACEMENT FIELDS IN THE CORE THAT WAS BASED ON THE SECOND FROSTIG'S MODEL. FULLY DYNAMIC EFFECTS OF THE SOFT CORE AND FACE-SHEETS WERE CONSIDERED IN THIS INVESTIGATION. IMPACTS WERE ASSUMED TO OCCUR SIMULTANEOUSLY AND NORMALLY OVER THE TOP FACE-SHEET WITH ARBITRARILY DIFFERENT MASSES AND INITIAL VELOCITIES. THE CONTACT FORCES BETWEEN THE PANEL AND IMPACTORS WERE TREATED AS THE INTERNAL FORCES OF THE SYSTEM. IN THIS PAPER, NONLINEAR CONTACT STIFFNESS WAS LINEARIZED WITH A NEWLY PRESENTED IMPROVED ANALYTICAL METHOD. NUMERICAL RESULTS OF THE MENTIONED STRUCTURES WERE COMPARED WITH FINITE ELEMENT MODEL USING ABAQUS CODE.

Forced Resonant Vibrations and Self-Heating of Solids of Revolution Made of a Viscoelastic Piezoelectric Material

The concept of complex characteristics is used to formulate the coupled nonlinear boundary-value thermoelectroviscoelastic problem of the forced harmonic vibrations and self-heating of inelastic three-dimensional bodies of revolution taking into account the nonlinearity due to the dependence of the mechanical and electrical characteristics on temperature. An iteration method is used to reduce this nonlinear problem to a linear electroviscoelastic problem and a linear heat-conduction problem with a known heat source, which are solved using the finite-element method. This approach is used to solve a coupled nonlinear thermoelectroviscoelastic problem of the forced harmonic vibrations and self-heating of a hinged sandwich cylindrical panel. The numerical data obtained are analyzed, and the effect of nonlinearity on the amplitude–frequency and temperature–frequency responses is studied

A parametric study on the stress analysis and transient response of thick-laminated-faced cylindrical sandwich panels with transversely flexible core

In the present work the effects of important parameters such as core thickness, radius of curvature and sector angle on the static and dynamic response of composite cylindrical sandwich panels have been investigated using a higher-order sandwich panel theory (HSAPT). The presented higher-order theory, which applies first-order shear deformation shell theory (FSDT) for the face sheets and the equivalent elasticity theory for the core, is a rigorous approach that includes the higher-order effects incurred by the nonlinearity of the in-plane and transverse displacements of core. Equations of motion along with associated boundary conditions are derived by using Hamilton's principle. For simply-supported panels closed-form solutions can be achieved by Navier techniques. However, for dynamic analysis, the solution is obtained in the time domain by implementing Newmark method. Finally numerical parametric studies are performed to provide some insight into the roles of key variables that influence the static and dynamic response of sandwich panels.

Non-linear transient and damping analysis of a long cylindrical sandwich panel with embedded SMA wires

In this work, nonlinear dynamic analysis of a cylindrical sandwich panel with embedded SMA wires in the face sheets is performed taking into account the instantaneous and spatial martensite phase transformation. The Boyd and Lagoudas one-dimensional SMA constitutive equation is used to model the pseudoelastic behavior of the shape memory alloy wires. Since the martensite volume fraction depends on the stress distribution, the governing equations and the phase transformation kinetic equations are coupled together and therefore an iterative method is employed to solve the highly nonlinear equations. Moreover, considering that the stress resultants generated by the martensite phase transformation in the wires are path dependent values, an incremental method is used to estimate the increment of the stress resultants at each time step. A new finite-element-based procedure is proposed and Newmark time integration method is used to solve the finite element equations. The results show a gradual decrease in the amplitude of vibration as long as the SMA wires do not reach a fully elastic condition. This feature is of great interest for the vibration suppression of structures especially that which is related to resonance phenomena. Finally, the effect of various parameters such sector angle, operating temperature, wire volume fraction, through the thickness location of the wires and different boundary conditions on the vibration amplitude and loss factor is investigated.

Linear and nonlinear parametric instability behavior of cylindrical sandwich panels subjected to various mechanical edge loadings

ABSTRACTLinear and nonlinear dynamic instability behavior of cylindrical sandwich panels subjected to combined static and dynamic nonuniform in-plane loadings is studied in this article. The core compressibility effects are considered in the model by assuming fourth and fifth order expansions for the transverse and tangential displacement of the core. The exact stress distributions within the panel are determined by panel prebuckling analysis for the applied parabolic and partial edge loadings. Galerkin's method is used to reduce the governing partial differential equations of the shell panel into a set of nonlinear ordinary differential equations. Dropping the nonlinear term, dynamic instability regions are obtained by solving the Mathieu-type differential equation by the method of Fourier series. The characteristics feature of the stable and unstable regions are investigated by linear and nonlinear time history responses and phase plots of the shell panel in those regions using Newmark's time integration. Incremental harmonic balance (IHB) method is used to study the nonlinear frequency amplitude responses of the cylindrical sandwich panels.

Numerical and exact models for free vibration analysis of cylindrical and spherical shell panels

The present paper shows a comparison between classical two-dimensional (2D) and three-dimensional (3D) finite elements (FEs), classical and refined 2D generalized differential quadrature (GDQ) methods and an exact three-dimensional solution. A free vibration analysis of one-layered and multilayered isotropic, composite and sandwich cylindrical and spherical shell panels is made. Low and high order frequencies are analyzed for thick and thin simply supported structures. Vibration modes are investigated to make a comparison between results obtained via the FE and GDQ methods (numerical solutions) and those obtained by means of the exact three-dimensional solution. The 3D exact solution is based on the differential equations of equilibrium written in general orthogonal curvilinear coordinates. This exact method is based on a layer-wise approach, the continuity of displacements and transverse shear/normal stresses is imposed at the interfaces between the layers of the structure. The geometry for shells is considered without any simplifications. The 3D and 2D finite element results are obtained by means of a well-known commercial FE code. Classical and refined 2D GDQ models are based on a generalized unified approach which considers both equivalent single layer and layer-wise theories. The differences between 2D and 3D FE solutions, classical and refined 2D GDQ models and 3D exact solutions depend on several parameters. These include the considered mode, the order of frequency, the thickness ratio of the structure, the geometry, the embedded material and the lamination sequence.

Aeroelastic analysis and active flutter suppression of an electro-rheological sandwich cylindrical panel under yawed supersonic flow

Supersonic flutter control of a three-layered sandwich curved panel of rectangular plan form with an adaptive electro-rheological fluid (ERF) core layer is investigated. The panel is excited by an arbitrary transient transverse load along with an arbitrary airflow yaw angle. The problem formulation is based on Kirchhoff–Love thin shell theory, the first order Kelvin–Voigt viscoelastic material model, and the linear quasi-steady Krumhaar's modified supersonic piston theory that accounts for both the panel curvature and flow yaw angle. The classical Hamilton's principle and the Galerkin method are used to set up the equations of motion which are then put in the state-space form. The effects of applied electric field, panel aspect ratio, panel shallowness angle, and airflow direction on the critical free stream static pressure are studied. Also, the aeroelastic response of the cylindrical panel excited by an impulsive central point load is calculated using the Runge–Kutta time integration scheme. Subsequently, a Sliding Mode Control (SMC) methodology is implemented to actively attenuate the structural response in the supersonic flow regime. Numerical simulations establish the effectiveness of the applied control configuration in successful suppression of the structural oscillations. The validity of results is demonstrated by rigorous comparisons with the existing data.

Free vibration analysis of sandwich cylindrical panel with functionally graded core using three-dimensional theory of elasticity

This paper presents an exact three-dimensional free vibration solution for sandwich cylindrical panels with functionally graded core. Material properties of the FGM core are assumed to be graded in the radial direction, according to a simple power-law distribution in terms of volume fractions of the constituents. Poisson’s ratio is assumed to be constant. The governing equation of motions is formulated based on the 3D-theory of elasticity and displacement fields are expanded in Fourier series along the in-plane coordinates which satisfy the simply supported edges boundary conditions. The state space technique is used to obtain natural frequencies analytically. Accuracy and convergence of the present approach are examined by comparing the analytical results with the existing values in literature. The parametric study is carried out to discuss the effects of gradient index, geometrical properties such as span angle, facing layers thickness and axial length to mid radius ratio on the frequency behavior of the sandwich panel. The obtained exact solution shows that the FGM core has significant effects on the vibration behavior of sandwich cylindrical panel. This fist known exact solution serves as a benchmark for assessing the validity of numerical methods or two-dimensional theories used to analyses of sandwich cylindrical panels.