Wing structural design: an approach with truss-based modular structures and metamodel-based optimization

Abstract

Disruptive projects and technologies have been presented with the aim of improving and reducing structural weight during aircraft design. With the replacement of fossil fuel by electric propulsive systems and, consequently, with the removal of fuel tanks from the wing’s inner structure, it is possible to rethink and develop new ways to optimize and reduce its weight. Therefore, based on the Common Research Model’s wingbox, this work aims to showcase the effectiveness of a truss-based inner structure in fulfilling this objective in commercial aircraft, bringing a new structural design approach, in which the conventional inner structures, such as ribs, spars, and stringers, are replaced solely by a truss-based one, and its joints are represented by mass elements. The linear static analysis of the structure is performed using NASTRAN as its solver, which in turn is integrated into a particle swarm optimization in MATLAB that optimizes the design variables of the optimization problem. Those include the outer radius and thickness of each truss of the structural mesh, which have their maximum and minimum bounds determined using a Kriging metamodel of the simplified wing structure. Boundary conditions are based on the original Common Research Model and an aerodynamic model that is able to determine the acting loads in different conditions. The possibility of removing unnecessary elements is also evaluated, while still ensuring the minimum aerodynamic profile necessary to form the wing. The wingbox structure is then optimized in search of the lowest structural weight considering stress constraints. The results, verified by a buckling and an aerodynamic flutter post-analyses, show that truss-based modular structures can be a good strategy in structural wing designs, in terms of modularity and reduction of weight.