Approximation of the critical buckling factor for composite panels

This article is concerned with the approximation of the critical buckling factor for thin composite plates. A new method to improve the approximation of this critical factor is applied based on its behavior with respect to lamination parameters and loading conditions. This method allows accurate approximation of the critical buckling factor for non-orthotropic laminates under complex combined loadings (including shear loading). The influence of the stacking sequence and loading conditions is extensively studied as well as properties of the critical buckling factor behavior (e.g concavity over tensor D or out-of-plane lamination parameters). Moreover, the critical buckling factor is numerically shown to be piecewise linear for orthotropic laminates under combined loading whenever shear remains low and it is also shown to be piecewise continuous in the general case. Based on the numerically observed behavior, a new scheme for the approximation is applied that separates each buckling mode and builds linear, polynomial or rational regressions for each mode. Results of this approach and applications to structural optimization are presented

An efficient application of Bayesian optimization to an industrial MDO framework for aircraft design

The multi-level, multi-disciplinary and multi-fidelity optimization framework developed at Bombardier Aviation has shown great results to explore efficient and competitive aircraft configurations. This optimization framework has been developed within the Isight software, the latter offers a set of ready-to-use optimizers. Unfortunately, the computational effort required by the Isight optimizers can be prohibitive with respect to the requirements of an industrial context. In this paper, a constrained Bayesian optimization optimizer, namely the super efficient global optimization with mixture of experts, is used to reduce the optimization computational effort. The obtained results showed significant improvements compared to two of the popular Isight optimizers. The capabilities of the tested constrained Bayesian optimization solver are demonstrated on Bombardier research aircraft configuration study cases

Aeroelastic Optimization of Variable Stiffness Composite Wing with Blending Constraints

Optimizing the laminates of large composite structures is nowadays well-recognized as having significant benefits in the design of lightweight structural solutions. However, designs based on locally optimized laminates are prone to structural discontinuities and enforcing blending during the optimization is therefore crucial in order to achieve structurally continuous and ready-tomanufacture designs. Bi-step strategies, relying on a continuous gradient-based optimization of lamination parameters followed by a discrete stacking sequence optimization step during which blending is enforced, have been proposed in the literature. However, significant mismatch between continuous and discrete solutions were observed due to the discrepancies between both design spaces. The present paper highlights the capability of the continuous blending constraints, recently proposed by the authors, in reducing the discrepancies between discrete and continuous solutions. The paper also demonstrates that more realistic optimal continuous designs are achieved thanks to the application of the blending constraints during the aeroelastic optimization of a variable stiffness wing. Additionally, the proposed blending constraints have been applied to NASTRAN SOL 200 showing their ease of implementation in commercial software.Aerospace Structures & Computational Mechanic

Implementation of Active and Passive Load Alleviation Methods on a Generic mid-Range Aircraft Configuration

The influence of passive and active load alleviation methods on the structure weight has been investigated on the wing of a Generic Mid-Range aircraft configuration. The models have been created with ModGen, an in-house program at DLR-AE (Institute of Aeroelasticity, DLR German Aerospace Center). The models comprise FE-models for the structure and masses, as well as DLM (Doublet-Lattice-Method) model for the aerodynamics. For the investigation of the influence of the loads alleviation systems a loop of loads analyses and subsequent structure sizing has been conducted. The loads analyses consist of gust and maneuver simulations. For the passive loads alleviation an aeroelastic tailoring of the wing structure has been implemented, whereas for the active loads alleviation the ailerons are deflected to redistribute lift during maneuvers and to partially compensate lift increment during gust encounters

Implementation of active and passive loads alleviation methods on a generic mid-range aircraft configuration

Loads analysis and structural design are core steps of the aircraft design process. To reduce wing loads and with it the wing structural mass, methods of passive and active loads alleviation have been researched in recent years. However, those methods are currently implemented without the consideration of dynamic simulations or unsteady aerodynamics in the optimization process in aircraft predesign. The purpose of this research is to investigate the influence of passive and active loads alleviation methods on the structural mass in aircraft preliminary design. The methods have been applied on the wing of a Generic Mid-Range (GMR) aircraft configuration. The models have been created with ModGen, an in-house program at DLR Institute of Aeroelasticity. The models comprise FE-models for the structure and masses, as well as DLM (Doublet-Lattice-Method) model for the aerodynamics. For the investigation of the influence of the loads alleviation systems, a loop of loads analysis and subsequent structure optimization has been conducted. The loads analysis consists of gust and maneuver simulations. For the passive loads alleviation, an aeroelastic tailoring of the wing structure has been implemented, whereas for the active loads alleviation the ailerons are deflected to redistribute lift during maneuvers and to partially compensate lift increment during gust encounters. With the implemented methods, a first quantification of the influence of loads alleviation methods on the structural mass in aircraft predesign is possible.Aerospace Structures & Computational Mechanic

Multidisciplinary Design Optimisation Research Contributions from the AMEDEO Marie Curie Initial Training Network

This paper reviews the key research activities and results produced during the AMEDEO (Aerospace Multidisciplinarity-Enabling Design Optimisation) Marie Curie Initial Training Network (ITN). AMEDEO brought together optimisation researchers and practitioners from European universities, research organisations, multinationals and SMEs to develop innovative Multidisciplinary Design Optimisation (MDO) methods for the design of energy-efficient aircraft. A range of new results are presented in the areas of: 1) efficient High Performance Computing techniques for MDO, 2) efficient metamodel-based robust MDO frameworks, 3) the application of advanced MDO methods to aircraft engine design and 4) novel applications of MDO to the design of composite aeronautical structures. The future challenges that need to be overcome to embed MDO methods more effectively within commercial design cycles in the aerospace industry are also briefly discussed