STABILITY OF FUNCTIONALLY GRADED HYBRID COMPOSITE PLATES

This paper presents a formulation of the stability problem for a recta ngular composite plate reinforced by two types of fibers, one of them being both stiffer and more expensive than the other. An obvious desig n solution based on cost containment is to concentrate stiffer and mor e expensive fibers in the area of the plate where they can provide a m aximum benefit to its stability. In the present paper, the stiffer fib ers replace a certain fraction of ''ordinary'' fibers in the layers of the plate oriented along the load direction. Moreover, a distribution of the volume fraction of these fibers across the width of the corres ponding layers is nonuniform (piece-wise distribution). The goal is to maximize the buckling load subject to the constraint on the total cro ss-sectional area of the stiffer fibers. The solution can be obtained exactly by integrating the equation of equilibrium for each plate regi on where the stiffnesses are constant and satisfying the continuity an d boundary conditions. Another approach, which is employed in this pap er, is based on the Galerkin procedure. Numerical examples illustrate a possibility of a significant enhancement of the buckling load using functionally graded hybrid composite plates.