OPTIMAL-DESIGN OF HYBRID LAMINATES WITH DISCRETE PLY ANGLES FOR MAXIMUM BUCKLING LOAD AND MINIMUM-COST

The design of hybrid symmetric laminated plates consisting of high-sti ffness surface and low-stiffness core layers is presented. In the firs t problem the maximization of buckling load is carried out over a disc rete set of ply angles. In the second problem the minimum number of hi gh-stiffness plies is determined for a given buckling load to minimize the material cost. Boolean variables are introduced to specify stacki ng sequence. Solution of the linear optimization problem yields an opt imal stacking sequence. The effect of hybridization is investigated fo r various problem parameters such as the aspect ratio of the laminate and the number of plies. The optimal designs are obtained with upper b ound constraints on the effect of bending-twisting coupling stiffnesse s. Results are given for hybrid graphite-epoxy/glass-epoxy laminates u nder both uniaxial and biaxial loadings.