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Thermoelastic vibration characteristics of asymmetric annular porous reinforced with nano-fillers microplates embedded in an elastic medium: CNTs Vs. GNPs

Arshid Ehsan, Amir Saeed, Loghman Abbas

Archives of Civil and Mechanical Engineering

2023

Vol. 23, no. 2

art. no. e100, 2023

Due to the vast usage of metal foam structures in branches of science, reinforcing them with nano-fillers makes them more convenient. Hence, in the current study, vibration characteristics of functionally graded porous nanocomposite (FGPN) annular microplates are taken into consideration. Two kinds of nano-fillers, namely Carbon nanotubes (CNTs) and Graphene nanoplatelets (GNPs), are selected as the reinforcements to analyze and compare their effect on the microstructure’s vibrational response. The mentioned nano-fillers are dispersed according to four patterns which affect various mechanical properties of the structure. Similarly, based on given functions which are called porosity distributions, pores are placed in thickness course of the microstructure. Then, its properties are determined via employing Halpin-Tsai and extended rule of mixture micromechanics models. Using the first-order shear deformation theory (FSDT), modified couple stress theory (MCST), and Hamilton’s principle for dynamic systems, governing motion equations and related boundary conditions are derived in asymmetric state, and then, they are solved, and natural frequencies and corresponding mode shapes are extracted with the help of generalized differential quadrature method (GDQM). By validating the results in simpler conditions, effects of the most important parameters are examined. It is found that GNPs are more effective in reinforcing the structure than CNTs. Also, about 15~18 percent reduction in frequencies is seen by increasing the porosity up to seventy percent.

Free vibration and buckling analyses of FG porous sandwich curved microbeams in thermal environment under magnetic field based on modified couple stress theory

Arshid Ehsan, Arshid Hossein, Amir Saeed, Mousavi S. Behnam

Archives of Civil and Mechanical Engineering

2021

Vol. 21, no. 1

89--111

Porous sandwich structures include different numbers of layers and are capable of demonstrating higher values of strength to weight ratio in comparison with traditional sandwich structures. Free vibration and mechanical buckling responses of a three-layered curved microbeam was investigated under the Lorentz magnetic load in the current study. A viscoelastic substrate was considered and the effect of the thermal environment on its mechanical properties was assessed. The core was composed of the functionally graded porous materials whose properties changed across the thickness based on some given functions. The face sheets were FG-carbon nanotube-reinforced composites and the influence of the placement of CNTs was evaluated on the behavior of the faces. Using the extended rule of mixture, their effective properties were determined. Modified couple stress theory was used to predict the results in the micro-dimension. While the governing equations were derived based on the higher order shear deformation theory and energy method, and mathematically solved via Navier’s method. The results were validated with the previously published works, considering the effects of various parameters. As comprehensively explained in the results section, natural frequencies and critical buckling loads were reduced by enhancing the central opening angle. Moreover, an increase in the porosity coefficient declined the mentioned values, but increasing the CNTs content showed the opposite effect. The outcomes of this study may help in the design and manufacturing of various equipment using such smart structures, making high stiffness to weight ratios more accessible.