Vibration and damping analysis of layered isotropic twisted blades

A layered triangular plate element with six degrees of freedom per node is presented. This element has been used to analyse vibration and damping characteristics of pre-twisted cantilever blades. The damping layer is assumed to be made of a viscoelastic material, the elastic modulus of which is expressed in complex form. A parametric study is conducted to study the influence of twist angle, aspect ratio, layer thickness and skew angle on the natural frequencies and loss factors of the system. The variation in non-dimensional frequencies of a layered blade 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 the first flexural frequency.