Nonlinear Damping Characteristic of Nanocomposite Beams Via Dynamical Analysis

The nonlinear dynamical behavior of nanocomposite beams made of polybutylene terephthalate and branched carbon-nanotube (CNTs) are experimentally investigated. The frequency response curves of specimens with different CNTs weight fractions are obtained in cantilever configurations by applying a base excitation and measuring the tip displacement. The stationary response of the beams is acquired for different excitation levels in order to capture the nonlinear trend for increasing oscillation amplitudes. In particular, the additional damping provided by the interfacial stick-slip between CNTs and hosting matrix determines a softening response in the small oscillation range exhibited by the reduction of the lowest resonance frequency followed by a hardening trend at higher amplitudes. The experimental results are identified by employing a closed-form solution of the stationary response based on a hysteretic nonlinear beam model.