Fiber contribution to modal damping of polymer matrix composite panels

An analytical method to determine the modal frequencies and damping of flexural vibration of continuous fiber-reinforced composite panels has been developed. Fiber damping effects are included in this method. Damped panel vibration modes are found using a higher-order laminate theory and the Rayleigh-Ritz method with complex eigenvalue analysis. Fiber contribution to modal damping was found to be significant in vibration modes involving longitudinal deformation of fibers. For a [0]₈ P100/3501-6-square cantilevered laminate, in vacuum and at room temperature (20° C), the predicted first mode damping showed an increase of 77 % by including fiber damping. The use of bromine-intercalated P100 fibers resulted in a further predicted increase of 438 % in the first mode damping at room temperature. Effects of changes in ply orientation, temperature, and thickness of the laminate on the fiber contribution to damping were examined. Fiber contribution to the damping of an angle-ply laminate can be estimated from the mode shapes and ply orientation of the laminate. Damping of modes exhibiting nearly pure bending or a combination of bending and twisting can be significantly improved by use of treated (intercalated) fibers.