COMPARISON OF BEAM AND PLATE THEORIES FOR FREE-VIBRATIONS OF METAL-MATRIX COMPOSITE PRETWISTED BLADES

Vibration characteristics of pre-twisted metal matrix composite blades are analyzed by using beam and plate theories. A beam element with ei ght degrees of freedom per node has been developed with torsion-flexur e, flexure-flexure and shear-flexure couplings which are encountered i n twisted composite beams. In the bean analysis, reduced three-dimensi onal constitutive relations are used. A triangular plate element prese nted in the literature is used for the composite material to model the beam as a plate structure. Both the theories have been validated for the isotropic case. This paper summarizes the quantitative comparison of natural frequencies of composite blade obtained by these theories. A parametric study is carried out for both the beam and plate elements results, the parameters being twist angle, fiber orientation, taper r atio and lamination scheme. (C) 1996 Academic Press Limited