scholarly journals Hygrothermal environment effect on the critical buckling load of FGP microbeams with initial curvature integrated by CNT-reinforced skins considering the influence of thickness stretching

2021 ◽  
Vol 10 (1) ◽  
pp. 1140-1156
Author(s):  
Mohammad Alkhedher
Keyword(s):  
Couple Stress Theory ◽  
Shear Deformation Theory ◽  
Functionally Graded ◽  
Buckling Load ◽  
Polar Coordinates ◽  
Curved Beams ◽  
Virtual Displacement ◽  
Initial Curvature ◽  
The Core ◽  
Hygrothermal Environment

Abstract Due to the need for structures with refined properties to bear against different loading conditions, recently, carbon nanotubes (CNTs) have been used widely to reinforce them. The extremely high stiffness of CNTs makes them significant as one of the best reinforcements to improve the mechanical behaviors of structures. This work focuses on microbeam buckling response with an initial curvature that includes three layers. The mid-layer that is known as the core is constituted of functionally graded porous (FGP) materials and two CNT-reinforced composite skins are bonded to the core to integrate it. The whole structure is affected by the hygrothermal environment and springs and shear layers are put below it. For the first time, for such a structure, a refined shear deformation theory (RSDT) as a higher-order theory that considers thickness stretching effect in polar coordinates is used that presents more accurate results, especially for deeply curved beams. Modified couple stress theory (MCST) in combination with the virtual displacement principle is utilized to establish the governing equations. The obtained results demonstrate the significance of porosity percentage and CNTs’ addition to the skins on the critical nanotubes buckling load. Also, the different behaviors of the microstructure at various temperatures are analyzed and discussed in detail.

Functionally graded viscoelastic core characteristics on vibroacoustic behavior of double-walled cylindrical shells in a subsonic external flow

2022 ◽  
pp. 107754632110467
Author(s):  
Shohreh Reaei ◽  
Roohollah Talebitooti
Keyword(s):  
Cylindrical Shell ◽  
Transmission Loss ◽  
Excitation Frequency ◽  
Shear Deformation Theory ◽  
Sound Transmission ◽  
Functionally Graded ◽  
Loss Coefficient ◽  
Sound Transmission Loss ◽  
Polymeric Foam ◽  
The Core

The present study is concerned with an analytical solution for calculating sound transmission loss through an infinite double-walled circular cylindrical shell with two isotropic skins and a polymeric foam core. Accordingly, the two-walled cylindrical shell is stimulated applying an acoustic oblique plane wave. The equations of motion are derived according to Hamilton’s principle using the first-order shear deformation theory for every three layers of the construction. Additionally, by the aid of employing the Zener mathematical model for the core of polymeric foam, mechanical properties are determined. To authenticate the results of this study, the damping of the core layer goes to zero. Therefore, the numerical results in this special case are compared with those of isotropic shells. The results prove that the presented model has high accuracy. It is also designated that decreasing the power-law exponent of the core leads to improving the sound transmission loss through the thickness of the construction. Besides, in addition to probe some configurations versus alterations of frequencies and dimensions, the convergence algorithm is provided. Consequently, it is realized that by increasing the excitation frequency, the minimum number of modes to find the convergence conditions is enhanced. The results also contain a comparison between the sound transmission loss coefficient for four different models of a core of a sandwiched cylindrical shell. It is comprehended that the presented model has a transmission loss coefficient more than the other types of the core at high frequencies.

scholarly journals Internal Energy Transfer in Dynamical Behavior of Slightly Curved Shear Deformable Microplates

2015 ◽  
Vol 11 (4) ◽  
Author(s):  
Mergen H. Ghayesh ◽  
Hamed Farokhi ◽  
Gursel Alici
Keyword(s):  
Energy Transfer ◽  
Internal Energy ◽  
Couple Stress Theory ◽  
Dynamical Behavior ◽  
Shear Deformation Theory ◽  
Initial Imperfection ◽  
Modal Interactions ◽  
Initial Curvature ◽  
Out Of Plane ◽  
Transfer Mechanisms

This paper investigates the internal energy transfer and modal interactions in the dynamical behavior of slightly curved microplates. Employing the third-order shear deformation theory, the microplate model is developed taking into account geometric nonlinearities as well as the modified couple stress theory; the initial curvature is modeled by an initial imperfection in the out-of-plane direction. The in-plane displacements and inertia are retained, and the coupled out-of-plane, rotational, and in-plane motion characteristics are analyzed. Specifically, continuous models are developed for kinetic and potential energies as well as damping and external works; these are balanced and reduced via Lagrange's equations along with an assumed-mode technique. The reduced-order model is then solved numerically by means of a continuation technique; stability analysis is performed by means of the Floquet theory. The possibility of the occurrence of modal interactions and internal energy transfers is verified via a linear analysis on different natural frequencies of the system. The nonlinear resonant response of the system is obtained for the cases with internal energy transfer, and energy transfer mechanisms are analyzed; as we shall see, the presence of an initial curvature affects the system dynamics substantially. The importance of taking into account small-size effects is also shown by discovering this fact that both the linear and nonlinear internal energy transfer mechanisms are shifted substantially if this effect is ignored.

Bending analysis of sandwich plates with composite face sheets and compliance functionally graded syntactic foam core

2016 ◽  
Vol 230 (20) ◽  
pp. 3606-3630 ◽  
Author(s):  
Mohammad Javad Lashkari ◽  
Omid Rahmani
Keyword(s):  
Plate Theory ◽  
Theory Of Elasticity ◽  
Functionally Graded ◽  
Shear Stresses ◽  
Rectangular Plates ◽  
Governing Equations ◽  
Positive Role ◽  
Virtual Displacement ◽  
The Core ◽  
Composite Face

In this paper, the problem of a rectangular plate with functionally graded soft core and composite face sheets is considered using high order sandwich plate theory. This theory applies no assumptions on the displacement and stress fields in the core. Face sheets were treated using classical theory and core was exposed to the theory of elasticity. Governing equations and boundary conditions are derived using principle of virtual displacement and the governing equations are based on eight primary variables including six displacements and two shear stresses. This solution is able to present localized displacements and stresses in places where concentrated loads are exerted to the structure since the displacements in the core can take a nonlinear form which could not be seen in the previous theories such as classical and higher order shear theories. This theory is suitable for rectangular plates under all types of loadings distributed or concentrated which can be different on upper and lower face sheets at the same point. The results were compared with the published literature using theory of elasticity and showed good agreement confirming the accuracy of the present theory. Subsequently, the solution for the core with functionally graded material is presented and effectively indicates positive role of functionally graded core.

scholarly journals Mechanical Buckling Analysis of Saturated Porous Functionally Graded Elliptical Plates Subjected to In-Plane Force Resting on Two Parameters Elastic Foundation Based on HSDT

2020 ◽  
Vol 142 (4) ◽  
Author(s):  
Mohammad Hossein Sharifan ◽  
Mohsen Jabbari
Keyword(s):  
Elastic Foundation ◽  
Ritz Method ◽  
Shear Deformation Theory ◽  
Potential Energy Function ◽  
Buckling Analysis ◽  
Functionally Graded ◽  
Buckling Load ◽  
Critical Buckling Load ◽  
Mechanical Buckling ◽  
Two Parameters

Abstract In this paper, mechanical buckling analysis of a functionally graded (FG) elliptical plate, which is made up of saturated porous materials and is resting on two parameters elastic foundation, is investigated. The plate is subjected to in-plane force and mechanical properties of the plate assumed to be varied through the thickness of it according to three different functions, which are called porosity distributions. Since it is assumed that the plate to be thick, the higher order shear deformation theory (HSDT) is employed to analyze the plate. Using the total potential energy function and using the Ritz method, the critical buckling load of the plate is obtained and the results are verified with the simpler states in the literature. The effect of different parameters, such as different models of porosity distribution, porosity variations, pores compressibility variations, boundary conditions, and aspect ratio of the plate, is considered and has been discussed in details. It is seen that increasing the porosity coefficient decreases the stiffness of the plate and consequently the critical buckling load will be reduced. Also, by increasing the pores' compressibility, the critical buckling load will be increased. Adding the elastic foundation to the structure will increase the critical buckling load. The results of this study can be used to design more efficient structures in the future.

scholarly journals Elastic Wave Characteristics of Graphene Reinforced Polymer Nanocomposite Curved Beams Including Thickness Stretching Effect

Polymers ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2194 ◽  
Author(s):  
Pouyan Talebizadehsardari ◽  
Arameh Eyvazian ◽  
Farayi Musharavati ◽  
Roohollah Babaei Mahani ◽  
Tamer A. Sebaey
Keyword(s):  
Elastic Wave ◽  
Strain Gradient ◽  
Effective Properties ◽  
Virtual Work ◽  
Shear Deformation Theory ◽  
Functionally Graded ◽  
Opening Angle ◽  
Small Scale ◽  
Curved Beams ◽  
Wave Characteristics

This work aims at analyzing elastic wave characteristics in a polymeric nanocomposite curved beam reinforced by graphene nanoplatelets (GNPs). GNPs are adopted as a nanofiller inside the matrix to enhance the effective properties, which are approximated through Halpin-Tasi model and a modified rule of mixture. A higher-order shear deformation theory accounting for thickness stretching and the general strain gradient model to have both nonlocality and strain gradient size-dependency phenomena are adopted to model the nanobeam. A virtual work of Hamilton statement is utilized to get the governing motion equations and is solved in conjunction with the harmonic solution procedure. A comparative study shows the effects of small-scale coefficients, opening angle, weight fraction, the total number of layers in GNPs, and wave numbers on the propagation of waves in reinforced nanocomposite curved beams. This work is also developed for two different distribution of GNPs in a polymeric matrix, namely uniformly distribution and functionally graded one.

Thermoelastic Vibration of Shear Deformable Functionally Graded Curved Beams with Microstructural Defects

2018 ◽  
Vol 18 (11) ◽  
pp. 1850135 ◽  
Author(s):  
Mohammad Amir ◽  
Mohammad Talha
Keyword(s):  
Material Properties ◽  
Volume Fraction ◽  
Shear Deformation Theory ◽  
Functionally Graded ◽  
Opening Angle ◽  
Curved Beams ◽  
Microstructural Defects ◽  
Thermoelastic Vibration ◽  
Benchmark Solutions ◽  
Shear Deformable

In the present study, the thermoelastic vibration of shear deformable functionally graded material (FGM) curved beams with microstructural defects (porosity) has been analyzed by the finite element method. The formulation is based on the higher-order shear deformation theory. The material properties of FGM beams are allowed to vary continuously in the thickness direction by a simple power-law distribution in terms of the volume fractions of the constituents. Even and uneven distributions of porosities in the beam have been considered with temperature-dependent material properties. Comparison and convergence study has been performed to validate the present formulation. Parametric studies have been done to study the effect of different influencing parameters on the frequency of the FGM curved beam, i.e. porosity, temperature rise, volume fraction index and opening angle. Some new results are presented which can be used as benchmark solutions for future research.

Temperature-dependent vibration analysis of a FG viscoelastic cylindrical microshell under various thermal distribution via modified length scale parameter: a numerical solution

2017 ◽  
Vol 26 (1-2) ◽  
pp. 9-24 ◽  
Author(s):  
Hamed Safarpour ◽  
Kianoosh Mohammadi ◽  
Majid Ghadiri
Keyword(s):  
Boundary Conditions ◽  
Scale Parameter ◽  
Couple Stress Theory ◽  
Differential Quadrature Method ◽  
Equations Of Motion ◽  
Shear Deformation Theory ◽  
Functionally Graded ◽  
Length Scale Parameter ◽  
Length Scale ◽  
Temperature Dependent

AbstractIn this article, the vibrational analysis of temperature-dependent cylindrical functionally graded (FG) microshells surrounded by viscoelastic a foundation is investigated by means of the modified couple stress theory (MCST). MCST is applied to this model to be productive in design and analysis of micro actuators and micro sensors. The modeled cylindrical FG microshell, its equations of motion and boundary conditions are derived by Hamilton’s principle and the first-order shear deformation theory (FSDT). For the first time, in the present study, functionally graded length scale parameter which changes along the thickness has been considered in the temperature-dependent cylindrical FG microshell. The accuracy of the present model is verified with previous studies and also with those obtained by analytical Navier method. The novelty of the current study is consideration of viscoelastic foundation, various thermal loadings and size effect as well as satisfying various boundary conditions implemented on the temperature-dependent cylindrical FG microshell using MCST. Generalized differential quadrature method (GDQM) is applied to discretize the equations of motion. Then, some factors are investigated such as the influence of length to radius ratio, damping, Winkler and Pasternak foundations, different temperature changes, circumferential wave numbers, and boundary conditions on natural frequency of the cylindrical FG microshell. The results have many applications such as modeling of microrobots and biomedical microsystems.

Dynamic stability of the double-bonded annular nanocomposite sandwich microplate on viscoelastic foundation

2021 ◽  
pp. 109963622110204
Author(s):  
Mohsen Emdadi ◽  
Mehdi Mohammadimehr
Keyword(s):  
Mechanical Properties ◽  
Dynamic Stability ◽  
Dynamic Instability ◽  
Couple Stress Theory ◽  
Shear Deformation Theory ◽  
Unit Cell ◽  
Core Material ◽  
Viscoelastic Foundation ◽  
The Core ◽  
Core Thickness

In this research, the dynamic stability of the double-bonded annular sandwich microplate is investigated. Face sheets are made from composite materials reinforced by carbon nanotubes in which mechanical properties are obtained by the extended rule of the mixture. Also, the core layer is made from a honeycomb aluminum which is defined by the geometric parameters of the unit cell and mechanical properties of the virgin core material. The equations of motion are derived from Hamilton’s principle and solved by the differential quadrature method (DQM) based on higher order shear deformation theory (HSDT) and modified couple stress theory (MCST). The results are compared with the obtained results by the other literature to examine the accuracy of the present formulation. The dynamic stability of the double-bonded annular sandwich microplate with hexagonal honeycomb core including variations of core thickness, inclined angle, and aspect ratio of the unit cell are discussed. Also, the effects of motion direction of the structure, viscoelastic foundation, material length scale parameter, volume fractions of CNTs in face sheets, and the core thickness to total thickness ratio on dynamic instability region are presented.

On the Analysis and Fundamental Frequency of Slightly Curved Sandwich Beams With a Delamination

1995 ◽  
Author(s):  
John N. Rossettos
Keyword(s):  
Shear Deformation ◽  
Fundamental Frequency ◽  
Transverse Shear ◽  
Transverse Shear Deformation ◽  
Sandwich Beams ◽  
Combined Effects ◽  
High Modulus ◽  
Curved Beams ◽  
Initial Curvature ◽  
The Core

Abstract An analysis of the vibration of sandwich beams with small iinitial curvature and a delamination between the core and face sheet is presented. The combined effects of initial curvature, transverse shear deformation and extent of delamination are evaluated and discussed. It is shown that the sensitivity to delamination damage is greater for straight beams than for initially curved beams. It is also greater for high modulus cores (less shear deformation). Also the influence of shear deformation on the fundamental frequency becomes smaller as the curvature increases.

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