Anbindung eines Lastanalyse Tools an das gradientenbasierte Strukturoptimierungstool lightworks

Das grundlegende Ziel der Arbeit ist die Auswahl und Anbindung eines Lastanalysetools an die gradientenbasierte Strukturoptimierung in lightworks. Dafür wurde auf Basis einer Literaturrecherche Lastanalyseverfahren und -tools untersucht. Für die Toolauswahl wurden Auswahlkriterien identifiziert und die Tools anhand dieser bewertet, sodass eines für die Anbindung ausgewählt werden konnte. Das Lastanalysetool soll für eine in CPACS gegebene Flugzeugdefinition die auf den Flügel wirkenden Kräfte und Momente berechnen können. Dabei sollen aerodynamische und (aero-) elastische Effekte berücksichtigt werden. Die Anbindung des ausgewählten Tools wird dargestellt und deren Funktionalität anhand eines Anwendungsbeispiels demonstriert und auf Plausibilität überprüft. Durch eine Variation der Elastizität der Flügelstruktur wird abschließend die Funktionalität der Kopplung zwischen Elastizität und Lasten demonstriert

Multidisciplinary optimization of an NLF forward swept wing in combination with aeroelastic tailoring using CFRP

This article introduces a process chain for Commercial aircraft wing multidisciplinary optimization (MDO) based on high fidelity simulation methods. The architecture of this process chain enables two of the most promising future technologies in commercial aircraft design in the context of MDO. These technologies are natural laminar flow (NLF) and aeroelastic tailoring using carbon fiber reinforced plastics (CFRP). With this new approach the application of MDO to an NLF forward swept composite wing will be possible. The main feature of the process chain is the hierarchical decomposition of the optimization problem into two levels. On the highest level the wing planform including twist and airfoil thickness distributions as well as the orthotropy direction of the composite structure will be optimized. The lower optimization level includes the wing box sizing for essential load cases considering the static aeroelastic deformations. Additionally, the airfoil shapes are transferred from a given NLF wing design and the natural laminar flow is considered by prescribing laminar-turbulent transition locations. Optimization results of the multidisciplinary process chain are presented for a Forward swept wing aircraft configuration on conceptual design level. The results show a fuel burn reduction in the order of 9% for the design mission

AN AUTOMATED ASSESSEMENT TOOL OF NLF CRITERIA FOR AIRFRAME JOINTS

An ever increasing awareness of the ecological impact of air travel and associated regulatory measures demands for a cut in aircraft fuel consumption to reduce CO2 emissions and operating costs. Among improvements in engine technology or use of alternative fuels, the sustainment of laminar flow on surface areas of transport aircraft is seen as an important contribution to the solution of this challenge. The reduced friction drag of a natural laminar flow (NLF) wing can lead to a reduction in fuel consumption and thus reduction of CO2 emissions of up to 8 % on aircraft level [1]. Laminar flow's sensitivity to surface disturbances however requires specific shapes and high surface quality: Structural features like steps, gaps and surface waviness can cause early laminar/turbulent transition [2]. This calls for novel structural design concepts for laminar flow applications and tools to enable their practical implementation in aircraft operation. Through the course of several national and EU-funded projects, a multi-material leading edge concept using CFRP with an integrally bonded steel foil erosion shielding is being developed by DLR [3] with a distinct focus on operability. The leading edge and an associated interchange-enabling attachment concept are realized in a 2.3 m ground based demonstrator representing an outer wing section. A test stand is designed to recreate "wing on ground" and "cruise flight" surface deformations to enable interchange trials of the leading edge [4]. To enable an assessment against NLF criteria of the achieved step at the joint between leading edge and wing cover, an automated step measurement tool is developed and verified against manual assessments. Such a tool is a necessary step not only to validate suitability to support NLF on aircraft wings of the leading edge design and attachment concept. It also serves as a key contribution to a possible closed loop system supporting the assembly of airframe structures with intended laminar flow characteristics by providing direct feedback of the surface quality and informing on necessary adjustments to be made by the technicians. The paper will focus on the development of the assessment tool, framed by the results it delivered on the NLF leading edge installation trials

Global aero-structural design optimization of composite wings with active manoeuvre load alleviation

In the scope of the DLR project VicToria (Virtual Aircraft Technology Integration Platform), an integrated process for aero-structural wing optimization based on high fidelity simulation methods is continuously developed and applied. Based upon a parametric geometry, flight performance under transonic flight conditions and manoeuvre loads are computed by solving the Reynolds-averaged Navier-Stokes equations. Structural mass and elastic characteristics of the wing are determined from structural sizing of the composite wing box for essential manoeuvre load cases using computational structural mechanics. Static aeroelastic effects are considered in all flight conditions and active manoeuvre load alleviation is integrated in the process. Global aero-structural wing optimizations are successfully performed for wings with and without active manoeuvre load alleviation. The active manoeuvre load alleviation is introduced with a simplified modelling of control surface deflections using a mesh deformation technique. The minimization of the fuel consumption for three typical flight missions represents the objective function. Wing optimizations are performed for variable and constant wing planform parameters as well as for wings with conventional composite wing box structure and for more flexible wings. The latter is accomplished by introducing modifications of the structural concept and the strain allowable. A significant mass reduction of the optimized wing box is obtained for wings with active manoeuvre load alleviation, resulting in a drop in fuel consumption of about 3%. For wing optimizations with the more flexible wing concept, the active manoeuvre load alleviation shows an additional reduction of the fuel consumption in the order of 2%. The wings with active manoeuvre load alleviation results in optimized wing geometries with increased aspect ratio and reduced taper ratio

Rapid transformation of lamination parameters into stacking sequences

Lamination parameter optimisation is a highly efficient type of composite optimisation. An equally efficient transformation of lamination parameters into stacking sequences is not yet available. This paper presents a general method for rapidly transforming lamination parameters into continuous stacking sequences. Systematic studies of the relationship between lamination parameters and stacking sequences provide a broad understanding of the transformation problem. An important finding is that multiple stacking sequences share the same lamination parameter set. The transformation is therefore not unique and has to account for multiple layup solutions. The layup retrieval algorithm uses primitive optimisation techniques to search for all optima in the layup space. Ply angles and layer numbers are hereby not restricted. In two representative examples, the authors show the algorithm's capabilities of finding all stacking sequence solutions of a twelve layer laminate and of finding multiple stacking sequence solutions for arbitrary layer numbers. This makes the algorithm applicable for stacking sequence retrieval, the last step in lamination parameter optimisation

High-Fidelity-based MDO: A Closer Look at the Selected Sub-Processes Overall Aircraft Design Synthesis, Loads Analysis, and Structural Optimization

Within the DLR project VicToria various high fidelity-based MDO processes were set-up as applicalble methods for aircraft design. Apart from aerodynamic optimization using high fidelity-based CFD analysis, the sub-processes overall aircraft design synthesis, loads analysis, and structural optimization were part of the MDO processes. The presented paper expounds such MDO sub-processes in order to exhibit their contributions and capabilities for the respected MDO process