The Development of Stress Constraints for Aeroelastic Gust Optimization

The consideration of gust loads in the conceptual design phase has historically been omitted due to computational complexity and cost. Modern computational resources and methods break down these outdated paradigms and next generation aircraft designs require the inclusion of complex physics earlier in the design process to provide feasible solution spaces. Using the mode acceleration method, the aeroelastic equations of motion are derived for a von Mises stress constraint and differentiated to provide sensitivities suitable for optimization. Additionally, the role of inertial relief is identified in the mode acceleration method and its impact is explored in the design optimization of simple tapered wing. Overall, the von Mises stress constraint sensitivities agreed with fourth-order finite-differences and proved suitable for optimization. Six optimization problems were performed to understand the effects of inertial relief and non-structural weight on the wing design. The non-structural weight behaved as expected for the free-free designs by increasing the structural weight to accommodate the additional weight, but clamped designs showed opposite trends. Inertial relief proved to play a significant role in the planform design and thickness distributions of the wing designs which necessitates the inclusion of inertial relief for the aeroelastic design of wings subject to a gust.