On generating stiffening layouts with density-based topology optimization considering buckling

This work includes a complete optimization, design, sizing and validation application of density-based topology optimization for a single stiffened panel from the upper skin of a commercial aircraft wing. In this work, topology optimization is carried with Optistruct from Altair. The initial values of the density variables are shown to have the biggest impact on the optimized material distribution. This effect is used in a random restart approach to explore multiple local minima, and thus to find different material distributions. Different material distribution obtained with topology optimization have shown the same buckling resistance within the implicit model used for optimization. However, the stiffened panel models created from the different material distributions show very different strength when they are sized with a subsequent optimization and validated using quasi-static non-linear analysis. Besides, the optimization results are almost all simple orthogrid solutions. Finding these layouts with topology optimization has proven to be difficult and highlights the fact that the technology is not mature for the design of new layouts for stiffened panels.