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New Achievements in Stability of Composite Airframe Structures

Degenhardt, Richard and Teßmer, Jan (2007) New Achievements in Stability of Composite Airframe Structures. In: Proceedings of the 12th Australian International Aerospace Congress. 12th Australian International Aerospace Congress, 2007-03-19 - 2007-03-22, Melbourne, Australien.



European aircraft industry demands for reduced development and operating costs, by 20% and 50% in the short and long term, respectively. Structural weight reduction by exploitation of structural reserves in composite aerospace structures contributes to this aim, however, it requires accurate and experimentally validated stability analysis of real structures under realistic loading conditions. This paper presents new achievements from the area of computational and experimental stability research of composite aerospace structures which contribute to that field. The first four topics focus on stringer stiffened panels and the last one on imperfection sensitive unstiffened cylinders. Section 1 presents new results achieved so far in the running EU (European) project COCOMAT, which deals with an accurate and reliable simulation of collapse. The main objective of COCOMAT is a future design scenario which exploits considerable reserves in fibre composite fuselage structures by accurate simulation of collapse. The project results comprise an experimental data base, improved slow and fast computational tools as well as design guidelines. Section 2 deals with validated postbuckling simulation of stiffened CFRP-panels by experiments. The validation procedure to ensure reliable numerical simulations requires extensive experimental data, especially in the case of nonlinear calculations with the possibility of several bifurcation and limit points in the postbuckling region. Therefore, the experiments have to be planned carefully, to ensure a reliable and goal-oriented validation with respect to the numerical analysis. Section 3 presents the fast tool IBuck for the simulation of the postbuckling behaviour. It is a semi-analytical tool for the simulation of axially loaded panels that are stiffened in both axial and circumferential direction. In today’s design process dynamic loading, e.g. due to gusts or landing impact, is assumed to be uncritical, since the dynamic process increases buckling stability. Section 4 shows that rapidly applied loading of stiffened panels can yield critical dynamic behavior in the postbuckling regime. When applying the new design philosophy it has either to be assured that these critical interactions do not occur under the loading velocities to be expected, or they have to be taken into consideration. Section 5 presents a recently developed approach for unstiffened shells which are usually susceptible to imperfections. This robust design approach is based on a single buckle as the worst imperfection mode leading directly to the load carrying capacity of a cylinder. It also promises to improve the knock-down factors which are according the current guidelines very conservative. Future work should facilitate full applicability of the analysis methods in preliminary design. For that purpose speed of the collapse analysis of stiffened panels needs to be increased and for collapse simulation degradation must be taken into account. The application field of the robust design method should be widened towards imperfection sensitive stiffened shells (skin-dominant designs).

Item URL in elib:https://elib.dlr.de/50318/
Document Type:Conference or Workshop Item (Paper)
Title:New Achievements in Stability of Composite Airframe Structures
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Date:19 March 2007
Journal or Publication Title:Proceedings of the 12th Australian International Aerospace Congress
Open Access:Yes
Gold Open Access:No
In ISI Web of Science:No
Keywords:Stability, Composite Structures, Buckling, Postbuckling, Collapse, Imperfection, Dynamic Loading, Robust Design
Event Title:12th Australian International Aerospace Congress
Event Location:Melbourne, Australien
Event Type:international Conference
Event Dates:2007-03-19 - 2007-03-22
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Aeronautics
HGF - Program Themes:Aircraft Research (old)
DLR - Research area:Aeronautics
DLR - Program:L AR - Aircraft Research
DLR - Research theme (Project):L - Structures & Materials (old)
Location: Braunschweig
Institutes and Institutions:Institute of Composite Structures and Adaptive Systems > Structural Mechanics
Deposited By: Ries, Doris
Deposited On:01 Nov 2007
Last Modified:31 Jul 2019 19:20

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