Vibration design of laminated fibrous composite plates with local anisotropy induced by short fibers and curvilinear fibers

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The present paper studies an optimum design method for proposing new types of fiber-reinforced composite plates with locally anisotropic structure. A finite element program is developed to analyze vibration of such locally anisotropic plates and the fundamental frequency is taken as an object function to be maximized. First, for demonstrating the effectiveness of local anisotropy, the optimum distributions of short fibers are calculated without directional constraints using a simple genetic algorithm (GA), and the layerwise optimization (LO) concept is used to reduce the computation time in the finite element calculation. Secondly, optimum arrangements of continuous curvilinear fibers are obtained under the continuity constraints where fibers directions are considered as projections of contour lines of a cubic polynomial surface. Numerical results show that the local anisotropy successfully improves frequency property and the optimum directions of short fibers indicate physically reasonable orientations. Also, the plates with optimally shaped continuous fibers yield higher fundamental frequencies than the conventional plates with parallel fibers.