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In this work, the dynamic behavior of the spherical magnetorheological elastomer (MRE) sandwich shell panel with multiwalled carbon nanotubes (MWCNT) reinforced composite face sheets is studied. The governing differential equation of motion for the (doubly curved) spherical sandwich shell panel is derived based on the Higher-Order Shear Deformation Theory (HSDT) kinematics. In the finite element framework, nine noded iso-parametric elements with nine Degrees of Freedom (DOFs) at each node are considered for solving the numerical problem. The finite element model of the multifunctional MR elastomer core spherical sandwich shell panel is validated against the existing works in terms of natural frequencies on different boundary conditions and magnetic field environment. The influence of MWCNT in the face sheet of the MR elastomer spherical sandwich shell panel is also studied through the structural rigidity. Detailed parametric investigations are performed to study the stiffness and damping characteristics of the shell panel with respect to the magnetic field intensities, thickness ratio, aspect ratio, ply orientation, and boundary conditions on the multifunctional MR elastomer core spherical sandwich shell panel. Also, the transverse vibration study of the MWCNT reinforced spherical sandwich shell with MR elastomer is carried out for different magnetic field intensities and curvatures to assess their effects on the structural performance. This study shows the applicability of the MR elastomer in sandwich shell structure for control of vibration and damping.

In the present study, the vibration analysis of a multiwalled carbon nanotubes (MWCNTs)-reinforced composite shell is performed to investigate the enhancement in natural frequencies and damping of polymer composite structure. Initially, the material characterization of MWCNT-reinforced polymer resin was performed using scanning electron microscope, transmission electron microscope, and energy-dispersive X-ray analysis to identify the bonding behavior of MWCNT with resin, structure of MWCNTs, structural integrity, and chemical purity of MWCNT. The mechanical characterization of MWCNT-reinforced polymer composites was performed using universal testing machine to identify the enhancement in tensile properties of the composites with MWCNT reinforcement. Laminated composite shell samples were then fabricated with the different weight fraction of the MWCNT to study the effect of weight percentage of MWCNT on the composite shells on enhancement of natural frequencies and damping. Significant increase in tensile characteristics of the composites could also be identified with the addition of MWCNT in polymer composites. It was also observed that the fundamental natural frequency and damping factor of the hybrid composite could be increased by 20% and 7%, respectively, with 1 wt% reinforcement of MWCNT in the polymer resin.

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In this paper, the vibration analysis of uniform laminated composite sandwich beam with a viscoelastic core was studied. The governing equation of motion of the laminated composite sandwich beam has been derived based on higher order shear deformation theory (HSDT) in finite element model (FEM IntroductionNowadays the demand for the sandwich structure is getting increased because of its high stiffness to the low weight ratio. It is also paved the attention of the researchers and scientist towards the sandwich structures. A Sandwich structure finds its place in wide range of applications because of its high stiffness and flexural rigidity especially in marine, aerospace and astronautics. Ibrahim Ozkol and AytacArikoglu [1] were made an investigation on vibration analysis of the uniform laminated composite sandwich beams with viscoelastic core using differential transform method. The governing equation of motion of sandwich beamwas formulated by Hamilton's principle and it was solved by differential transform method (DTM), Eigen value analysis method was used to generate and evaluate frequencies. Banerjee et al. [3] investigated the vibration characteristics of the viscoelastic material based asymmetric sandwich beam by using the dynamic stiffness model which was developed from the Timoshenko beam theory. Manoharan et al. [4] presented the finite element formulation of the magnetorheological (MR) fluid based sandwich beam. The governing equation of motion sandwich beam was formulated using finite element method. In this study it was concluded that the natural frequencies increased by increasing the intensity of the magnetic field irrespective to the boundary conditions. Allahverdizadeh et al. [5] was studied the dynamic behaviour of adaptive sandwich beams, where the middle layer as electro-rheological fluid (ERF) and constraining layers were fabricated by functionally graded materials (FGM). This study shows that the resonant frequencies and the amplitude of peak values have been decreased by increasing the thickness FGM at constant electric filed. From the results it was indicated that at a definite applied electric field, the Clamped-Clamped beam showed the higher resonant frequencies and the cantilever beam showed the least value among all end conditions. Xu and Qiu [6] studied the free vibration analysis and optimization method of composite lattice truss core sandwich beams. The partial differential governing equation of motion was developed by adopting the Hamilton principle which was based on Thimosenko and bernoullis beam theory and then the natural frequencies of the