Static aeroelastic models with integrated stiffness-contributing shell structures built by additive manufacturing

The wind tunnel test of static aeroelastics is a basic method to study the static aeroelastic phenomena of aircraft and other similar structures. As the test objects, the static models need to meet similar requirements, such as geometric similarity and stiffness similarity. The traditional models adopt a spar-frame-skin hybrid structure. The multiple frame segments (skins) of the models are separated from each other, and it is difficult to ensure the geometrical similarity of the aerodynamic shapes of the models during the tests. The overall stiffness of the models with this structure is borne by the metal spars, which makes it difficult to design and manufacture the models. Replacing the segmented frame/skins in the hybrid structure, an integrated shell structure made of additive manufacturing technology (AM) that contributes partial stiffness is proposed in this paper. Based on the structure, a static aeroelastic model is designed in two phases: the similarity design and stiffness design. The stiffness design is formulated as a constrained single-objective optimization problem, and the gradient-based optimization algorithm is adopted to implement the optimization to obtained structural dimensions of the model in the hybrid structure. The errors of the stiffness design are checked and the contribution of integrated shell to the overall stiffness is discussed. A large-aspect-ratio aircraft is chosen as the prototype and a static aeroelastic model with the integrated resin shell is designed, calibrated, and tested in this paper. The results show that the static aeroelastic model with the proposed AM integrated shell is feasible and can be used to study the static aeroelastics reliably and efficiently.