Free vibration analysis of orthotropic plate has been investigated with the help of dynamic stiffness method using classical plate theory. The rectangular plates have two opposite edges simply-supported, while all possible combinations of free, simply-supported and clamped boundary conditions are applied to the other two edges. Hamilton's principle is used to derive the governing differential equations of motion and natural boundary conditions in free vibration. The dynamic stiffness matrix is

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... erived by relating the amplitudes of forces to those of the displacements at the plate ends. The Wittrick-Williams algorithm is used as the solution technique when applying the dynamic stiffness matrix to compute the natural frequencies and mode shapes.