Structural Optimization of Platelike Aircraft Wings Under Flutter and Divergence Constraints

Minimum-weight aircraft wing design, with an emphasis on avoiding aeroelastic instability, has been studied since the 1960s. The majority of works to date were posed as sizing problems; only a handful of researchers have employed a topology optimization approach. The aim of this study is to use the level set method for this purpose. The problem is formulated as one of plate thickness distribution, which takes on one of two prescribed values at every point on the wing planform. This is combined with constraints implemented on the eigenvalues of the flutter equation; such an approach is shown to be robust and versatile. Optimization results for rectangular plate wings at a range of sweep configurations studied previously are included to validate the present methods. Delta, high-aspect-ratio, and typical swept transport wing planforms are then optimized. All solutions demonstrate the ability to significantly reduce wing mass while maintaining flutter and divergence speed above a specified limit, which can be higher than that of the reference, maximum-thickness design. The proposed method can be used to provide insights into optimal aeroelastic wing structures and is particularly useful for developing unconventional aircraft structural configurations.