Adjoint-Based Structural Optimization of Aircraft Wings Subjected to Dynamic Loads

This talk presents the development of a framework to directly size and optimize a structure under dynamic loads with a special focus on early aircraft design. Low degrees of freedom (DoF) beam models are used in place of high DoF models to represent the structure, thereby significantly reducing the computational cost (runtime and memory). For a given residual system of equations, the adjoint method for time-dependent problems solved with the stable BDF will be shown to require computation of six terms. This generalization allows for the implementation of a generic, equation-agnostic adjoint solver. Constraint aggregation techniques are extended to both spatial and temporal domain to constraint the strength-based stress yield criterion throughout the dynamic simulation. The proposed structural analysis method is applied to the wing structural analysis and sizing of a novel hybrid-electric propulsion aircraft -- NASA's PEGASUS concept. It is shown that the sizing of aircraft wings for 14 CFR specified maneuvers 2.5g and -1.0g static maneuvers using the proposed approach produces a 6% difference in weight compared to a shell-based method, but with a 7.8x speed-up, and is efficient at sizing the wingbox structure for dynamic loads generated by dynamic gust maneuvers.