Multi-Disciplinary Design of Aircraft Fuselage Structures

Abstract

The fuselage structure of civil passenger transport aircraft has mechanical duties combined with the task to protect passengers against the cold and excessive noise in the different flight phases. Current design practice for fuselage structures is a sequential approach in which mechanical requirements are satisfied first after which the acoustical and thermal requirements are satisfied in a corrective fashion. It can be questioned if this approach will lead to an optimal weight design. Therefore a design study was started to compare sequential versus concurrent multi-disciplinary design of a simplified fuselage structure. A Design and Engineering Engine (DEE) has been built that is able to generate (input for) mechanical, acoustical and thermal models of stiffened and unstiffened simplified fuselage sections with optional floors subjected to mechanical, acoustical and thermal loads. So far the DEE was used to perform simple what-if studies. The DEE is now extended to optimize a stiffened cylinder for minimum weight, subjected to mechanical, acoustical and thermal constraints. The acoustical models have been validated with tests in which the predicted transmission loss is compared with the actual behavior of stiffened and unstiffened cylinders. Optimization is done using a SQP algorithm applied to response surfaces obtained with a DOE approach. The study shows that using MDO in this specific design problem can be beneficial to reduce weight.