A two-level optimization procedure for composite wing design subject to str
ength and buckling constraints is presented. At wing-level design, continuo
us optimization of ply thicknesses with orientations of 0 degrees, 90 degre
es, and +/-45 degrees is performed to minimize weight. At panel level, the
number of plies of each orientation (rounded to integers) and inplane loads
are specified, and a permutation genetic algorithm is used to optimize the
stacking sequence in order to maximize the buckling load. The process is s
tarted by performing a large number of panel genetic optimizations for a ra
nge of loads and numbers of plies of each orientation. Next, a cubic polyno
mial response surface is fitted to the optimum buckling load as a function
of the loads and numbers of plies of each orientation. The resulting respon
se surface is used for the wing-level optimization. Rounding and manual adj
ustment are used to obtain the final design. The procedure is demonstrated
using an example of a simple wing box design.