Interfacial Strain Energy Dissipation in Hybrid Nanocomposite Beams Under Axial Strain Fields

Abstract

A micromechanics and structural dynamics analysis of inherent damping exhibited by representative hybrid nanocomposite beams under axial strains is presented. The approximate model is used to assess the potential aeroelastic/aeromechanical stability enhancement of helicopter rotor blades from carbon nanotube matrix inclusions. The matrix/nanoinclusion micromechanics before the occurrence of interfacial slip are based on the Cox model for discontinuous fiber reinforcement, and the frictional energy dissipation is assumed to be proportional to the interfacial shear force where slip has occurred. The validity of the model is established by comparing with experimental measurements of storage and loss moduli for a polymer nanocomposite. The relatively simple model captures the salient features of nanocomposite interfacial slip energy dissipation once uncertainties in fiber orientation and dispersion are accounted for in an approximate manner by using an effective volume fraction. The validated model is then used to calculate damping of the first in-plane bending mode when a beam is subjected to axial strain fields representative of hingeless rotor blades. Results indicate that hybrid nanocomposites with nanoinclusions show significant potential for contributing to future vertical lift capabilities by augmenting rotorcraft aeromechanical stability margins of hingeless/bearingless rotors.