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In this study postbuckling behaviors of multiscale composite sandwich doubly curved piezoelectric shell with a flexible core and MR layers by employing Homotopy Perturbation Method in hygrothermal environment has been investigated. By using Reddy third shear deformable theory the face sheets and third-order polynomial theory of the flexible core the strains and stresses are obtained. A mathematical model for the multiscale composite layered shell with a flexible core and magnetorheological layer (MR) that incorporates the nonlinearity of the in-plane and the vertical displacements of the core is assumed. Three-phase composite shells with polymer/Carbon nanotube/fiber and polymer/Graphene platelet/fiber either uniformly or non-uniformly based on different patterns according to Halpin–Tsai model have been considered. The governing equations of multiscale shell have been derived by implementing Hamilton's principle. Meanwhile, simply supported boundary conditions are employed to the shell. For investigating correctness and accuracy, this paper is validated by other previous researches. Finally, different parameters such as temperature rise, various distribution patterns, magnetic fields and curvature ratio are considered in this article. It is found these parameters have significant effect on the frequency–amplitude curves. [ABSTRACT FROM AUTHOR]

In this research, thermal buckling and forced vibration characteristics of the imperfect composite cylindrical nanoshell reinforced with graphene nanoplatelets (GNP) in thermal environments are presented. Halpin–Tsai nanomechanical model is used to determine the material properties of each layer. The size-dependent effects of GNPRC nanoshell is analyzed using modified couple stress theory. For the first time, in the present study, porous functionally graded multilayer couple stress (FMCS) parameter which changes along the thickness is considered. The novelty of the current study is to consider the effects of porosity, GNPRC, FMCS and thermal environment on the resonance frequencies, thermal buckling and dynamic deflections of a nanoshell using FMCS parameter. The governing equations and boundary conditions are developed using Hamilton's principle and solved by an analytical method. The results show that, porosity, GNP distribution pattern, modified couple stress parameter, length to radius ratio, mode number and the effect of thermal environment have an important role on the resonance frequencies, relative frequency change, thermal buckling, and dynamic deflections of the porous GNPRC cylindrical nanoshell using FMCS parameter. The results of current study can be useful in the field of materials science, micro-electro-mechanical systems and nano electromechanical systems such as microactuators and microsensors. [ABSTRACT FROM AUTHOR]

In this present work the critical loading of magneto-electro-viscoelastic-hygro-thermal (MEVHT) piezoelectric nanoplates embedded in a viscoelastic foundation are investigated. Via two variable shear deformation plate theory displacement are obtained. The governing equations of nonlocal viscoelastic nanoplate are driven by using Hamilton's principle and solved by an analytical solution. A parametric study is presented to examine the effect of the nonlocal parameter, hygro-thermo-magneto-electro-mechanical loadings and aspect ratio on the critical loading of MEVHT nanoplates. It is found that the critical loading is quite important to the mechanical loading, electric loading and magnetic loading, while it is insensitive to the hygro-thermal loading. [ABSTRACT FROM AUTHOR]

In this research a nonlocal strain gradient plate model is introduced for hygro-thermo-mechanical buckling analysis of double-layered graphene sheets in elastic medium. For more accurate analysis of graphene sheets, the proposed theory contains two scale parameters related to the nonlocal and strain gradient effects. In fact, buckling load increment due to the strain gradient effect is neglected in all previous papers related to double-layer graphene sheets. Governing equations of a nonlocal strain gradient double-layer graphene sheet on elastic substrate are derived via Hamilton’s principle. Galerkin’s method is implemented to solve the governing equations for different boundary conditions. Effects of different factors such as hygro-thermal loading, nonlocal parameter, length scale parameter, elastic foundation, interlayer stiffness and boundary conditions on buckling characteristics a double-layer graphene sheet are studied. [ABSTRACT FROM AUTHOR]

This study employs the nonlocal and surface elasticity theories to explore the buckling characteristics of piezoelectric nanobeams incorporating flexoelectricity effects. Flexoelectricity represents the coupling between the strain gradients and electrical polarizations. Considering the flexoelectricity effects, the piezoelectric nanobeams can tolerate higher buckling loads compared with conventional ones, especially at lower thicknesses. Both nonlocal and surface effects are considered in the analysis of flexoelectrically actuated piezoelectric nanobeams in magnetic field for the first time. Hamilton’s principle is employed to derive the governing equations and the related boundary conditions which are solved applying an analytical-based solution. Comparison study is also performed to verify the present formulation with those of previous data. Numerical results are presented to investigate the influences of the flexoelectricity, nonlocal parameter, surface elasticity, temperature rise, beam thickness and various boundary conditions on the buckling characteristics of magnetically affected flexoelectric nanobeam. [ABSTRACT FROM AUTHOR]

In this paper, electromechanical buckling behavior of size-dependent flexoelectric nanoplates is investigated based on nonlocal and surface elasticity theories. Flexoelectricity represents the coupling between strain gradients and electrical polarizations. Flexoelectric nanoplates can tolerate higher buckling loads compared with conventional piezoelectric nanoplates, especially at lower thicknesses. The flexoelectric nanoplate is in contact with a two-parameter elastic foundation, which consists of infinite linear springs and a shear layer. Nonlocal elasticity theory of Eringen is applied in the analysis of flexoelectric nanoplates for the first time. The residual surface stresses which are usually neglected in the modeling of flexoelectric nanoplates are incorporated into nonlocal elasticity to provide better understanding of the physics of the problem. Applying an analytical solution which satisfies various boundary conditions, the governing equations obtained from Hamilton's principle are solved. The reliability of the present approach is verified by comparing the obtained results with those provided in literature. Finally, the influences of nonlocal parameter, surface effect, plate geometrical parameters, elastic foundation and boundary conditions on the buckling characteristics of flexoelectric nanoplates are explored. [ABSTRACT FROM AUTHOR]