VIBRATION AND DAMPING ANALYSIS OF LAYERED ISOTROPIC TWISTED BLADES

A layered triangular plate element with six degrees of freedom per nod e is presented. This element has been used to analyse vibration and da mping characteristics of pre-twisted cantilever blades. The damping la yer is assumed to be made of a viscoelastic material, the elastic modu lus of which is expressed in complex form. A parametric study is condu cted to study the influence of twist angle, aspect ratio, layer thickn ess and skew angle on the natural frequencies and loss factors of the system. The variation in non-dimensional frequencies of a layered blad e is similar to that of an unlayered blade for aspect ratios of 1 and 2. The loss factor decreases with an increase of the twist angle for t he first flexural frequency.