Size-Dependent Torsional Buckling of Carbon Nano-Peapods Based on the Modified Couple Stress Theory

Abstract

Using the modified couple stress theory and the shell model, this paper investigates the torsional instability of carbon nano peapods (CNPs), which are the hybrid structures made by inserting C[Formula: see text] fullerenes into CNT. Based on the modified couple stress theory as a higher order elasticity theory and using the first-order shear deformation shell theory, the equilibrium equations are derived through the principle of the minimum potential energy. The critical torsional moment is determined for the (10,10) CNT and the C[Formula: see text]@(10,10) CNP, and compared with that of MD simulations in the literature. Then, the increase in critical torsional moment is represented with the increase in the length scale parameter in both (10,10) CNT and C[Formula: see text]@(10,10) CNP based on the modified couple stress theory. Besides, by comparing the critical torsional moment in the C[Formula: see text]@(10,10) CNP and the (10,10) CNT, 100 percent increase in buckling resistance due to the presence of C[Formula: see text] fullerene is exhibited as well. In addition, the CNP surrounding is modeled as Pasternak foundation, and the effects of Pasternak stiffness are shown on the critical torsional moment.