An experimental study on the nonlinear free vibration response of epoxy and carbon fiber-reinforced composite containing single-walled carbon nanotubes

Abstract

In this paper, the effects of additives of a single-walled carbon nanotube (SWCNT) on the nonlinear free vibration of neat resin and carbon fiber reinforced polymer composites (CFRPs) are investigated experimentally. To establish this purpose a sensitive noncontact setup is designed and prepared. In order to obtain a proper SWCNT dispersion pattern, a simple multistage method is presented to fabricate and test nanocomposite beams. First, the increase in the Young's modulus of the nanocomposites by adding carbon nanotube is investigated using the mechanical bending test and validated with available test results. Next, the nonlinear free vibration behavior of cantilever beams under small to large-deflection is investigated. The results of the vibration tests indicate that the nonlinear vibration behavior of all models is close to homogenous materials with increasing SWCNT. The results also show that transverse initial excitation (displacement) imposed an axial load on the slender beams, which thus leads to an increase in the nonlinear frequency of oscillation. In addition, the increase in frequency bears a relation to the initial displacement. Also, large initial displacements, especially on models without carbon fiber (reinforced epoxy), cause that the convergence of frequencies under different initial excitation did not occur. The results of this study show that adding SWCNT can lead to convergences of frequencies’ hybrid composites and reinforced epoxy during final cycles.