A Reliability-Based Multidisciplinary Approach for the Design Optimization of Very Flexible Wings

Nicolò Coccon, Ugo Galvanetto

University of Padova


The need for better performance and lower costs is becoming a major requirement for aeronautic structures. In particular, high-performance aircraft tend to be light and slender, with a consequent reduced induced drag, but also increased sensitiveness to detrimental aeroelastic phenoma.
Furthermore, the demand for lower costs is unavoidably connected to the concept of risk. Take structural design for example, sources of risk include prediction errors arising from design model assumption, and uncertainties both in material properties and load conditions. In the present work we propose a new approach to the reliability-based design optimization (RBDO) of high aspect ratio wings, where a nonlinear structural model of the wing is combined with an unsteady aerodynamic
model. In this optimization process, the aforementioned uncertainties are taken into account by a set of probabilistic constraints on the maximum allowable stress and strain as well as on the minimum structural frequencies, while the objectives of the analysis are mass minimization and prevention of aeroelastic instabilities. At the convergence of the optimization, the design variables will provide the optimal location of the elastic axis along the wing span, which meets the simultaneous requirements for optimizing the structure and attaining the desired levels of reliability on the probabilistic constraints.