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dynamic testing and analysis of extension-twist-coupled composite tubular sparsThe results from a study aimed at improving the dynamic and aerodynamic characteristics of composite rotor blades through the use of extension-twist elastic coupling are presented. A set of extension-twist-coupled composite tubular spars, representative of the primary load carrying structure within a helicopter rotor blade, was manufactured using four plies of woven graphite/epoxy cloth 'prepreg.' These spars were non-circular in cross section design and were therefore subject to warping deformations. Three cross-sectional geometries were developed: square, D-shape, and flattened ellipse. Results from free-free vibration tests of the spars were compared with results from normal modes and frequency analyses of companion shell-finite-element models developed in MSC/NASTRAN. Five global or 'non-shell' modes were identified within the 0-2000 Hz range for each spar. The frequencies and associated mode shapes for the D-shape spar were correlated with analytical results, showing agreement within 13.8 percent. Frequencies corresponding to the five global mode shapes for the square spar agreed within 9.5 percent of the analytical results. Five global modes were similarly identified for the elliptical spar and agreed within 4.9 percent of the respective analytical results.
Document ID
19940035864
Document Type
Conference Paper
Authors
Lake, Renee C.
(U.S. Army, Aerostructures Directorate; NASA, Langley Research Center Hampton, VA, United States)
Izapanah, Amir P.
(Vigyan, Inc.; NASA, Langley Research Center Hampton, VA; NASA, Ames Research Center, Moffett Field, CA, United States)
Baucon, Robert M.
(NASA Langley Research Center Hampton, VA, United States)
Date Acquired
August 16, 2013
Publication Date
January 1, 1992
Publication Information
Publication: In: International Modal Analysis Conference, 10th, San Diego, CA, Feb. 3-7, 1992, Proceedings. Vol. 2 (A94-12476 02-39)
Subject Category
STRUCTURAL MECHANICS
Distribution Limits
Public
Copyright
Other