Minimum cost design of vibrating laminates by hybridization

Antisymmetric, angle-ply laminates are optimized with the objective of minimizing the material costs by hybridization. The designs are subject to a lower bound on the fundamental frequency and to a total thickness constraint. The laminates are constructed as sandwich-type hybrids with inner layers made of low-stiffness fiber composite material and outer layers of a high-stiffness fiber composite material. The optimal designs for minimizing the material costs are obtained by hybridizing the laminates so that only a minimum amount of the high-stiffness layers are used to satisfy the minimum frequency requirement. The laminates are also optimized with respect to fiber orientations to improve their cost-effectiveness further. The numerical results are given for graphite/glass hybrid laminates and the effect of various problem parameters on the cost is discussed. The material cost of the hybrid construction is shown to be several times less than that of a graphite laminate.