Experimental results were obtamed for the natural frequencies and the mode shapes of graphite-epoxy and boron-epoxy composite materials having fiber orientations of 0°, 15°, 30° and 90° with respect to cantilever beam axes Certain elastic constants were experimentally determined and used in a programmed numerical solution in which rotary inertia, trans verse shear, and coupled bending-torsion effects were included. The experi mental results for the 15° and 30° beams gave a clear indication of the interaction between bending and twisting and good agreement was obtained with the numerical results.
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