Application of composite rotor blade stability analysis to extension-twist coupled blades

A finite element based stability analysis is developed for a hingeless, composite, isolated rotor in hover. It includes a mechanism for the inclusion of a complete 6 x 6 stiffness matrix, as well as the effects of rotary inertia. No restrictions are made on the magnitudes of the displacements and rotations if the magnitudes of the strains remain small compared to unity. The equilibrium position is obtained by an iterative solution of the complete nonlinear equations. The dynamic equations are linearized about this position, yielding and eigenproblem. The lift model is a two-dimensional, quasi-steady strip theory, with inflow taken from momentum theory. Initial results are given for the stability of extensiontwist coupled rotor blades.