Coupled Composite Rotor Blades under Bending and Torsional Loads

This paper presents an analytical-cum-experimental study of the structural response of composite rotor blades with elastic couplings. Vlasov theory is expanded to analyze two-cell composite rotor blades made out of general composite laminates including the transverse shear deformation of the cross­section. In order to validate this analysis, two-cell graphite-epoxy composite blades with bending­torsion coupling were fabricated using matched-die molding technique. These blades were tested under tip bending and torsional loads, and their structural response in terms of bending slope and twist was measured with a laser optical system. Good correlation between theory and experiment is achieved. The slenderness ratio of the blade controls the difference in single-cell and two-cell predictions. For blades with a slenderness ratio of 36, single-cell predictions overestimate the bending and torsional flexibilities by 87% and 41%, respectively.