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Proceedings Paper

Passive approach of controlling twist in composite tilt-rotor blades
Author(s): John B. Kosmatka; Renee C. Lake
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Paper Abstract

This paper examines the static and dynamic behavior of initially twisted composite spars for tilt-rotor applications, as well as documenting the fabrication of five pairs of initially twisted advanced composite single-cell spars. Spars having five different material stacking sequences were fabricated for a given geometric and pretwist definition so as to determine the maximum and minimum spar untwist for a given unit load (stiffness approach) and a given maximum load (strength approach). Analytical static stiffness and strength results are presented using a detailed shell-type finite element model, along with a two-dimensional elasticity approach to show how the maximum elastic beam untwist varies as a function of the composite spar geometric parameters and material ply orientation. Experimentally measured free-free and cantilevered natural frequencies and damping levels of the spars are presented along with a correlation to a highly refined shell-type finite element model. These vibration results reveal that both ply angle orientation and initial twist significantly alter the spar natural frequencies, where the effects are largest in the higher bending and torsion modes. Damping level changes were clearly observed with ply orientation changes (i.e. increases in extension-torsion coupling produced bending mode damping increases and torsion mode damping decreases).

Paper Details

Date Published: 1 May 1996
PDF: 12 pages
Proc. SPIE 2717, Smart Structures and Materials 1996: Smart Structures and Integrated Systems, (1 May 1996); doi: 10.1117/12.239076
Show Author Affiliations
John B. Kosmatka, Univ. of California/San Diego (United States)
Renee C. Lake, U.S. Army Research Lab. and NASA Langley Research Ctr. (United States)

Published in SPIE Proceedings Vol. 2717:
Smart Structures and Materials 1996: Smart Structures and Integrated Systems
Inderjit Chopra, Editor(s)

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