The uncoupled equation of motion for the flexural displacement of an orthotropic composite circular plate having symmetric lamination is presented. A numerical method is employed to calculate the symmetric and nonsymmetric vibrational frequencies of full and annular composite plates subjected to a variety of boundary conditions. Effects produced by lamination interchange and fiber reversal are discussed; in particular, certain laminations are capable of producing a higher fundamental frequency than either of the constituent materials alone can attain. For annular plates it is found that for certain lay-ups the fundamental frequency derives from a nonsymmetric mode. Finally, pinhole-center annuli are examined and, for a free inner edge, a comparison is made with corresponding full-plate frequencies.
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Greenberg et al. (1979) studied this question.