ON THE PREDICTION OF GEOMETRIC NONLINEAR EFFECTS ON THE DAMPING OF COMPOSITE STRIPS AND BEAMS: THE CASE OF BUCKLING

A theoretical framework is presented for analyzing the small-amplitude free-vibrational response of composite strips exhibiting significant geometric nonlinearities. Nonlinear GreenLagrange strains are introduced into the governing equations, assuming a Kelvin viscoelastic solid. A novel beam finite element is developed, which yields new nonlinear damping and stiffness matrices of the structure. The beam element is capable of predicting the damped free-vibration response and the modal characteristics of an in-plane deflected composite strip. Numerical results quantify the geometric nonlinear effect of compressive in-plane loads and the variation of modal damping and natural frequencies of composite strips during buckling and postbuckling response. Experimental measurements of a cross-ply Glass/Epoxy beam subject to buckling were conducted and correlated with the finite element predictions.