Structural and aeroelastic design optimization of truss-based modular wing structures

Abstract

This work studies a new design approach and structural and aeroelastic optimization of wings using truss-based modular structures. Due to pollutant emission reduction targets and the high demand for increasingly lighter and more efficient aircraft, this research topic has become very relevant today, becoming a relevant contribution to new approaches to aeronautical design. In this context, the idea of using modular structures comes with the promise of efficient manufacturing and reduced maintenance costs. Thus, the work proposes a new approach to structural topology, eliminating traditional elements, such as spars and ribs, and replacing them with modular truss-based structures, which are connected by spherical joints at their ends. The topological mesh of the structures are created from the Delaunay triangulation and tessellation. The structural model is based on two types of finite elements: beam and quadrilateral elements. The beam elements are defined from consistent Timoshenko elements and the quadrilaterals are based on Mindlin-Reissner kinematics using bi-linear interpolation and reduced integration to prevent shear locking. The Doublet-Lattice Method is used to predict the unsteady subsonic aerodynamics, and the P-K method is used to compute the aeroelastic system solution. For the examples and case studies, a reference wing geometry from the FLEXOP project is used as a baseline. Two optimizations are proposed, where in all the objective functions are to minimize the structural weight of the wing and to maximize the flutter speed. The first optimization has as design variables the number of control points, or nodes, in each airfoil and the number of sections along the span. In the second optimization, the external diameters and thicknesses of each of the modular structures are individually optimized, even eliminating unnecessary ones. The results show that it is possible to obtain relatively light wings that meet the structural and aeroelastic requirements; however, the definition of the optimization parameters directly influence the mesh generation and computational cost of the optimization. Above all, modular structures have proved to be a good strategy in the design of structures for new wing concepts.