EFFECTS OF DELAMINATIONS ON THE DAMPED DYNAMIC CHARACTERISTICS OF COMPOSITE LAMINATES - ANALYSIS AND EXPERIMENTS

Analytical and experimental work is presented on the damped free vibra tion of delaminated laminates and beams. A laminate theory is develope d in which the unknown kinematic perturbations induced by a delaminati on crack are treated as additional degrees of freedom. The generalized stiffness, inertia and damping matrices of the laminate are formulate d. An analytical solution is developed for the prediction of natural f requencies, modes and modal damping in composite beams with delaminati on cracks. Evaluations of the mechanics on various cantilever beams wi th a central delamination are performed. Experimental results for the modal frequencies and damping of composite beams with a single delamin ation are also presented and correlations between analytical predictio ns and measured data are shown. The effects of delamination vary based on crack size, laminate configuration and mode order. The implication s of the mechanics in developing delamination detection techniques are also discussed. (C) 1996 Academic Press Limited