Influence of flexural-torsional couplings and rotational effects on vibration behaviour of tapered thin-walled anisotropic biconvex beam

Accurate modelling and prediction of dynamic characteristics for rotating thin-walled blades have drawn attention as it is an essential part of structural health monitoring for various engineering and civil applications such as wind turbine, helicopter and aeroplane blades. With the advent of structural tailoring techniques, various non-classical effects and couplings implicitly affecting the behaviour of such structures are yet not fully explored. In this regard, the present work proposes a numerical model for finding the free vibration characteristics of anisotropic tapered biconvex closed cross-section beam under rotating conditions. The model is derived based on energy method following the Ritz approximation. Circumferentially asymmetric stiffness (CAS) ply configuration is considered in order to study the impact of flexural torsional coupling on the vibration characteristics. Transverse shear effects, primary and secondary warping were also included in the current model. Mode switching phenomenon is dissected elaborately for the first few frequencies under rotating and nonrotating conditions. The impact of rotational effects like centrifugal acceleration, centrifugal warping, inertial warping on the first few frequencies is also demonstrated. An iterative technique is adapted to solve the equations having these rotational effects. Modal Assurance Criterion (MAC) is done in order to judge the consistency of the modes at different rotating speeds.