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In this article, theoretical modeling and vibration characteristics of a spinning double-blade beam assembly restricted by elastic supports are studied. Graphene nanoplatelet (GPL) reinforcement and porous foamed metal matrix are adopted to make up the assembly structure. Due to the nonuniformity of the porosity and graphene nanofillers, the material properties of the attached blades and beam are considered to change along the blade thickness and beam radius, respectively. They are obtained via the rule of mixture, the open-cell scheme and the Halpin-Tsai micromechanics model. These attached blades and beam are modeled in accordance with the Euler-Bernoulli beam theory and the Rayleigh beam theory, respectively. Via employing the Lagrange's equation, the equations of motion of the double-blade beam are derived. Then, the natural frequencies of the spinning nanocomposite double-blade beam are calculated by the substructure modal synthesis method and the assumed modes method. A detailed parameter analysis is performed to study the influences of dimension, distribution pattern and weight fraction of GPLs, distribution and coefficient of porosity, length and location of the blades, stiffness and location of supports, and spinning speed on the mechanical behaviors of the double-blade beam assembly. [ABSTRACT FROM AUTHOR]

This study aims to perform free vibration and buckling analyses of circular cylindrical shells made of three-dimensional (3D) graphene foam. Three kinds of porosity distribution are considered including two kinds of symmetrical distribution and uniform distribution. The Kirchhoff-Love shell theory is utilized to establish the mathematical model of 3D graphene foam (3D-GF) shells. Natural frequencies and buckling loads of the shells under various boundary conditions are obtained via the Rayleigh-Ritz method in conjunction with Chebyshev polynomials. Results show that the mechanical characteristics of the 3D-GF shells are significantly affected by the porosity coefficient and porosity distribution. Moreover, the effect of porosity coefficient is closely related to boundary conditions of the shells. It is also shown that as the porosity coefficient increases, the porosity distribution effect on the mechanical characteristics of 3D-GF shells becomes increasingly significant. [ABSTRACT FROM AUTHOR]

In this study, the thermo-hygro-mechanical bending and vibration of functionally graded material (FGM) microbeams with microporosity defect are investigated. The mathematical model of the system is developed by using the sinusoidal beam theory and the modified couple stress theory. Based on Hamilton's principle, the governing equations and boundary conditions of imperfect FGM microbeams are derived. Then, Navier's method is utilized to calculate the deflections and natural frequencies of the system. Analytical results are presented to illustrate the effects of the microporosity volume fraction, the microporosity distribution type, the power-law index, the temperature and the moisture on the static bending and free vibration of imperfect FGM microbeams. [ABSTRACT FROM AUTHOR]