The design of hybrid symmetric laminated plates consisting of high-stiffnes
s surface and low-stiffness core layers is presented. The maximisation of t
he fundamental frequency and frequency separation is performed over a discr
ete set of available ply angles. Minimum cost design using a hybrid constru
ction is determined subject to a constraint on the fundamental frequencies
or frequency separation. Boolean variables are introduced to specify stacki
ng sequences and to obtain an expression for the frequency which is linear
in terms of the design variables. Solution of the linear optimisation probl
em yields an optimal stacking sequence for the specified objective function
. The effect of hybridisation is investigated for various parameters of the
laminate such as the aspect ratio and the number of plies. Results are giv
en for hybrid graphite-epoxy/glass-epoxy laminates. (C) 2001 Elsevier Scien
ce Ltd. All rights reserved.