Analysis of Helicopter Blade Anisogrid Composite Spar

The paper presents the structural analysis of an anisogrid spar of the composite rotor blade of a medium helicopter in terms of strength, stiffness and stability taking into account the requirements of mass efficiency. The spar is made in the form of a lattice shell, in which the anisogrid arrangement of the ribs allows transferring the flows of normal forces to the longitudinal ribs and shear loads to the spiral ribs located at angles of ± 45 deg. It is shown that the hingless blade fastening scheme does not allow realizing the weight advantages of the anisogrid spar due to significant bending loads. The mass efficiency of the lattice structure of the blade spar can be attained by changing the structural design of the main rotor by introducing a horizontal hinge.