Rapid Generation and Assessment of Aircraft Structural Topologies for Multidisciplinary Optimization and Weight Estimation

TLDR: Algorithms for rapid generation of moderate-fidelity structural finite element models of air vehicle structures to allow more accurate weight estimation earlier in the vehicle design process have been developed.

Abstract: ‡Algorithms for rapid generation of moderate-fidelity structural finite element models of air vehicle structures to allow more accurate weight estimation earlier in the vehicle design process have been developed. Application of these algorithms should help to rapidly assess and generate many structural layouts before the start of the preliminary design phase and reduce weight penalties imposed when actual structure weights exceed those estimated during conceptual design. By defining the structural topology in a fully parametric manner, the structure can be mapped to arbitrary vehicle configurations being considered during conceptual design optimization. Recent enhancements to this approach include the porting of the algorithms to a platform-independent software language Python, and modifications to specifically consider morphing aircraft-type configurations. Two sample cases which illustrate these recent developments are presented. I. Introduction HE application of multidisciplinary optimization to aero-structural design of flight vehicle structures has been a topic of considerable attention in recent years. Computational mesh generation has advanced considerably and has been used to allow parametric aerodynamic design of vehicle shapes to be considered in this optimization process. However, the structural layout design has not been typically treated with the same level of detail. In most cases, the structural layout is fixed and only a structural sizing optimization is performed. In the few instances where the layout is considered as a variable itself, the model chosen is usually overly simplistic, not representative of actual vehicle designs, and suspect from an accuracy perspective. Aircraft manufacturers have very accurate structural models of existing vehicles, but these models take literally months to generate and are not suitable for rapid consideration of candidate designs. Thus, there is a need for a methodology to create structural models of at least intermediate fidelity while incorporating the ability to generate these models automatically based on a parametric description of the structural layout. This will facilitate the application of these models to rapid generation and assessment of candidate external vehicle shapes. As a first step towards developing this automatic model generation capability, an abstraction of the aircraft structural elements and their layout was constructed so that models could be created quickly for a given structural layout regardless of changes in external shape. This abstraction was based on a thorough study of structural design trends in modern aircraft of various types 1 . Based on this abstraction, some initial algorithms to allow mapping of parametric structural topologies to arbitrary wing shapes were developed. These algorithms allow a structural designer to specify a layout in parametric terms, specifying locations in percentages of span and chord rather than actual dimensions. This specification is independent of the aircraft geometry so that upon making a change to the