STRUCTURAL BEHAVIOR OF 2-CELL COMPOSITE ROTOR BLADES WITH ELASTIC COUPLINGS

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 cross section. Variation of shear stiffness along the contour of the section is included in the warping function. To validate this analysis, two-cell graphite-epoxy composite blades with extension-torsion coupling were fabricated using a 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 was achieved. Axial force-induced twist rate of the order of 10 deg per meter length (0.25 deg per inch length) due to a 4.45-kN (1000-1b) force can be realized in extension-torsion coupled blades with a hygrothermally stable lay-up [20/ - 70]2s for potential applications in the design of till rotors.