J. John, L. Gaugelhofer, C. Hackner, J. Cumiskey, I. Yavrucuk

Helicopter structures are heavily influenced by vibration, often forcing structural changes late in the design process. While structural dynamics simulations may not always provide accurate results, flight testing remains often the only method to identify dynamic interactions and excitations. This is particularly relevant for new, innovative designs where practical experience is limited. One potential approach to mitigate design risks is to improve the damping of the aircraft structure. Natural fibers such as flax could be a promising approach. However, additional flax material is required to achieve stiffness and strength comparable to carbon components, resulting in increased weight. The aim of this study is to investigate how this weight increase can be minimized while still achieving optimal damping levels. To accomplish this, knowledge gained from the hybridization of simple specimens and cross-sectional laminates has been extended to a 3D laminate configuration. The goal is to develop structures with matching dynamic properties, minimal weight increase, and significant damping improvement. The influencing parameters of this strategy were first tested on double-T beams. High-strain regions were targeted for extensive hybridization to maximize damping, while low-strain regions received minimal hybridization to avoid excessive weight gain. As a practical demonstration, this approach was applied to a horizontal stabilizer. Emphasis was placed on the critical first bending modes, both asymmetrical and symmetrical. The dynamic properties of the structures, including damping and stiffness, were measured by experimental modal analysis. The results illustrate the feasibility of designing hybrid components with comparable dynamic behavior, demonstrating significantly improved damping properties with only a minor increase in weight. For example, the damping in the first symmetrical bending mode of the horizontal stabilizer was more than quadrupled while maintaining the same natural frequency and adding less than 10% of mass.

49th European Rotorcraft Forum 2023, Bückeburg, 2023

Conference Paper

englisch

21,0 x 29,7 cm, 28 Seiten

DGLR-Bericht, 2023, 2023-01, 49th European Rotorcraft Forum 2023 - Proceedings; S.1-28; 2023; Deutsche Gesellschaft für Luft- und Raumfahrt - Lilienthal-Oberth e.V., Bonn

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2023