Multidimensional models for double-swept helicopter blades

This paper presents multidimensional finite element models for the analyses of modern helicopter blades. The methodology enables finite elements with different dimensionality to be joined together in a consistent fashion. The formulation exploits the unique feature of a special class of refined beam elements, which have pure displacements as unknowns. This property makes it possible to connect beam and solid elements at node levels without the need for complicated mathematical formulations. Various problems in the modeling of realistic blades can be tackled with ease such as the application of nonclassical constraints. All physical surfaces of the structure can be modeled regardless of which finite element is used for discretizing the blade portion. Thus, three-dimensional stress states can be readily obtained by avoiding further postprocessing operations. The multidimensional models have been verified with experimental results and validated with beam and shell finite element solutions available in the literature by considering tip-swept blades with rectangular cross sections. The methodology has been then applied to a double-swept blade with a realistic profile.