Multidisciplinary optimization system for the detailed design of lightweight structures.

From the very beginning, no other subjects had such a strong impact on aviation as the development of lightweight structures and efficient propulsion systems. Improvements in these two areas result in immediate benefits for the performance of an aircraft in respect to payload, range and fuel consumption. Together with engineers from Airbus Defence and Space, the RISC Software GmbH has been working for more than 8 years on the development of a software system to calculate optimum weight designs and constructions of aircraft structures. Of particular importance is that design decisions for the overall structure regarding geometry and material can already be considered in a very early design phase, since the design options are greatest at this point and the greatest potential for weight savings is hence available.

To make this possible, Airbus Defence and Space has developed the multidisciplinary structural optimization system Lagrange, which helps designing minimal weight structures with respect to a broad set of different kinds of design parameters. Examples of design parameters include cross-sections of individual components or entire component groups, as well as layer thicknesses, layer angles, and individual paths of fibre composite materials.

Besides the design goal of reaching a minimum weight for a structural element, a variety of different mechanical and physical constraints are to be considered at the same time. The Lagrange optimization system provides a wide range of multidisciplinary criteria models. Thus, in addition to a series of mechanical strength and stability criteria, other restrictions as, for example, on natural frequencies, flutter speeds or transient aero-elastic responses can be formulated.

An essential capability for automating the overall design process is a coupled aero-structure analysis (aero-elasticity). Therefore, in addition to the dimensioning of structural elements during optimization, also aerodynamic loads can be actively influenced as part of the design process.

Moreover, Lagrange enables the consideration of special manufacturing constraints for composite materials, thus ensuring that the designs can be manufactured with the available methods. Already at the beginning of the design phase, this enables the computation of very realistic preliminary designs, whose models include several thousand design variables and several hundred thousand constraints.

Since 2009, the RISC Software GmbH has been the main development partner for the new development of central system parts of the Lagrange system. Of particular importance is the implementation of the latest, most efficient mathematical algorithms and the best use of modern hardware platforms, particularly with respect to parallel and distributed
computer architectures.