STAR-SHAPE CROSS-SECTION EXTENSION-TWIST-COUPLED COMPOSITE BEAMS FOR ROTORCRAFT APPLICATIONS

A novel extension-twist-coupled composite beam cross sectional configuration is proposed and analyzed in this work, characterized by increased torsional and bending rigidities compared to flat strips but having the same high level of extension-twist coupling. An analytical modeling of response is obtained by generalizing, based upon symmetry considerations, an existing model for the response of extension-twist coupled composite flat strips subject to finite deformation. A finite element analysis is performed for a set of selected configurations and the results show excellent correlation with the predictions of the analytical model, confirming both the generalization of the analytical model and the expected benefits of the proposed beam configuration. A testing program, currently in progress, is undertaken to experimentally verify the analytical and finite element results by manufacturing and testing, using an air bearing apparatus, a set of extension-twist coupled composite beams.