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Viscoelastic damping optimization of fuselage vibrations in aircraft

Sentongo, Gerald (2020) Viscoelastic damping optimization of fuselage vibrations in aircraft. DLR-Interner Bericht. DLR-IB-AE-GO-2020-171. Master's. Hochschule für Angewandte Wissenschaften Hamburg. 108 S.

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The focus of this thesis is the damping optimization of Constrained Layer Damping (CLD) treatments with viscoelastic materials (VEM) under mass constraints. The frequency dependent material properties of VEMs are characterised by a complex modulus. Under the assumption of Hooke’s law, the 1D-material model is transformed into a 3D-material model allowing for FE-calculations. Utilizing analytical models, the influence of the material and geometric properties on the modal loss factor of the first bending mode is analysed in a parameter study. It is demonstrated that the thickness of the core and constraining layers are possible design variables for damping optimization. Furthermore, an optimization process is established to determine optimal geometric parameters for damping maximization under predefined mass constraints. For this purpose, a Grid-Element-Generator is implemented in MATLAB and used for generating the associated FE-models. An interface to MSC Nastran solver is established for the analysis of the FE-model. Good agreements between analytical and numerical results confirm the applicability of the Nelder-Mead algorithm for damping optimization. Furthermore, the optimization algorithm is applied to a curved geometry of a highly simplified aircraft frame under free boundary conditions. The optimization is performed under predefined mass constraints for two different storage moduli representing two different temperature levels. A higher modal loss factor is achieved for a lower storage modulus. Considering different mass constraint, varying damping ratios are obtained for both storage moduli. As an alternative method for damping optimization, a cut-position optimization based on cutting of the core and constraining layers is performed. The results for the optimal location of the single cut contradict the rule of thumb established in literature. The optimal location of the single cut is dependent on the storage modulus of the VEM. Depending on the stiffness of a VEM, inserting a cut can either improve or reduce the damping effect.

Item URL in elib:https://elib.dlr.de/139624/
Document Type:Monograph (DLR-Interner Bericht, Master's)
Title:Viscoelastic damping optimization of fuselage vibrations in aircraft
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Date:November 2020
Refereed publication:No
Open Access:No
Gold Open Access:No
In ISI Web of Science:No
Number of Pages:108
Keywords:viscoelasticity, damping design, damping optimization, constrained layer damping
Institution:Hochschule für Angewandte Wissenschaften Hamburg
Department:Department Fahrzeugtechnik und Flugzeugbau
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Aeronautics
HGF - Program Themes:fixed-wing aircraft
DLR - Research area:Aeronautics
DLR - Program:L AR - Aircraft Research
DLR - Research theme (Project):L - Flight Physics (old)
Location: Göttingen
Institutes and Institutions:Institute of Aeroelasticity > Structural Dynamics and System Identification
Deposited By: Gröhlich, Martin
Deposited On:22 Dec 2020 15:52
Last Modified:22 Dec 2020 15:52

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