This paper documents the fabrication of five pairs of pretwisted advanced composite single-cell spars that are being used to experimentally demonstrate the extension-twist phenomena as a function of beam pretwist and composite material ply stacking sequence. 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). 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. Experimental/analytical results of the free-free and cantilevered spars 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. Experimentally measured frequency changes were greate than those predicted analytically using the finite element approach. 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).


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    Title :

    Experimental/analytical investigation of the free vibration behavior of composite spars with initial twist


    Additional title:

    Experimentell-analytische Untersuchung des freien Vibrationsverhaltens von Verbundstoffträgern mit Initialdrall


    Contributors:
    Kosmatka, J.B. (author) / Idosor, F.R. (author) / Lake, R.C. (author)


    Publication date :

    1995


    Size :

    8 Seiten, 9 Bilder, 3 Tabellen, 11 Quellen



    Type of media :

    Conference paper


    Type of material :

    Print


    Language :

    English




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