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Proceedings Paper

Development of an integral damping treatment for NASA's next-generation hollow fan blades
Author(s): John B. Kosmatka; Oral Mehmed
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Paper Abstract

A NASA research program is underway to develop fan blades that have significantly greater propulsive efficiency, lower acoustic noise, and lower weight. These blades have a large internal manifold and open trailing edge that is used to blow air in the downwash. The blades are composed of a titanium root and composite internal manifold with an outer graphite/epoxy shell. Due to the complex internal structure and open-cell design, these blades have low natural frequencies and bending-torsion coupled mode shapes that could potentially lead to aeroelastic instabilities. Increasing the damping levels in these blades will improve the fatigue life and reduce aeroelastic instability concerns. The vibratory modes of interest include the first and second bending modes as well as first torsion mode. Due to the geometric constraints of the outer blade shape and large internal manifold very little room is available for damping treatment placement. Results from the analysis study reveal that (1) significantly more damping can be obtained by embedding the material in the outer shells than within the manifold vanes, (2) carefully designing a patch that fills approximately 29% of the surface area and is only 0.005' thick will produce a loss factor of at least 0.01 for the first three structural modes, and (3) a patch that fills approximately 45% of the surface area will produce a loss factor of at least 0.02 for the first three structural modes.

Paper Details

Date Published: 27 June 2002
PDF: 10 pages
Proc. SPIE 4697, Smart Structures and Materials 2002: Damping and Isolation, (27 June 2002); doi: 10.1117/12.472662
Show Author Affiliations
John B. Kosmatka, Univ. of California/San Diego (United States)
Oral Mehmed, NASA Glenn Research Ctr. (United States)

Published in SPIE Proceedings Vol. 4697:
Smart Structures and Materials 2002: Damping and Isolation
Gregory S. Agnes, Editor(s)

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