Model-Based Aero-Structural Design and Optimization of a Highly Flexible High Aspect-Ratio Wing

This research presents the model-based aerostructural design process of the highly flexible composite wing and its optimization process. The parametric modeling of the wing was carried out using DLR’s ModGen, which generates all the essential features of the FE and Aero models of the wing. The models obtained are then integrated into the model-based design optimization framework, which seeks to minimize wing structural mass while maximizing structural flexibility with lower frequencies. This aligns with the core objective of the TU-Flex design, which is to develop a flying demonstrator with a wing bending frequency low enough to induce coupling with flight mechanics. Therefore, the spars of the Highly Flexible High Aspect-Ratio Wing are designed as the primary load-bearing structure, with minimal upper and lower skin thicknesses to minimize the wing bending frequency. The model-based design and optimization of the composite Wingbox is accomplished using a gradient-based optimization algorithm, with MSC Nastran. Three maneuvers (1g, 4g and -2g) as well as two gust cases (positive and negative) are considered to determine the optimal Wingbox design. The structural mass, the thickness distribution on the semi-span, the effectiveness of the control surface, and the elastic characteristics of the wing are derived from the structural optimization of the composite wing. The optimized wing shows a deformation of 8.9% under a 1g flight condition, while still meeting all the design feasibility requirements. Tip mass is necessary to be placed at the wing tip to further reduce the eigen frequencies of the wing - especially the first bending.