Abstract This study investigates the torsional vibration behavior of short fiber–reinforced (SFRC) nanotubes within the framework of doublet mechanics (DM) theory, while also accounting for viscoelastic material effects and flexible boundary conditions (BCs). The effective mechanical properties of the composite are estimated through the Halpin–Tsai nanomechanical model, and the Kelvin–Voigt approach is adopted to represent viscoelastic damping. A semi-analytical solution is developed by expressing the rotation field as a Fourier sine series and applying Stokes’ transformation, which enables the treatment of elastic torsional spring BCs in a unified manner. A key advantage of the proposed formulation is its flexibility: any combination of BCs—from fully clamped to completely free—can be handled simply by adjusting the spring stiffnesses without reformulating the governing equations. Numerical results reveal that damping has a significant effect on natural frequencies, particularly in higher vibration modes, where it can strongly suppress the dynamic response. Increasing the fiber volume fraction and aspect ratio enhances torsional stiffness and raises the frequencies, while a higher fiber-to-matrix mass density ratio leads to a slight decrease. The findings highlight the complex interplay between damping, scale effects, and nanostructural parameters, demonstrating that DM provides a robust higher-grade continuum framework for the dynamic analysis of reinforced nanostructures.
Akpınar et al. (Fri,) studied this question.