The mechanical characteristics of a laminated plate can be tailored by adjusting the fiber orientation angle of each orthotropic lamina. To find the fiber orientation angle of each lamina that maximizes the fundamental frequency, previous works analyses using various optimization algorithms have been performed so far. However, the solution space becomes significantly larger as the number of combinations in orientation angles increases. Thus the optimization process takes much more time. This

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... er sets up the orientation angles to discrete design variables, such as 15°, 30°, etc. Genetic algorithm is employed to find the optimal solutions. The CFRP rectangular composite plates with 8, 12 and 16 layers are considered as an example using the Ritz method for finding the eigenvalues. Two sets of classical boundary conditions are used as edge conditions. It was revealed that the fundamental frequency makes about 5% difference from the optimal value if it is in 30° steps and about 24% in 90° steps.