Linearized Frequencies and Damping in Composite Laminated Beams Subject to Buckling

Abstract

This paper considers the damped smallamplitude freevibration of composite laminated strips subject to large inplane forces and rotations. A theoretical framework is formulated for the prediction of the nonlinear damping of composite laminates subject to large Green–Lagrange axial strains and assuming a Kelvin viscoelastic solid. An extended beam finite element is developed capable of providing the nonlinear stiffness and damping matrices of the system. The linearized damped freevibration equations associated with the deflected strip shape in the preand postbuckling region are presented. Numerical results quantify the strong geometric nonlinear effect of compressive inplane loads on the modal damping and frequencies of composite strips. Measurements of the modal damping of a crossply glass/epoxy beam subject to buckling were also conducted and correlate well with the finite element predictions.