Experimental study of structural damping of composite helicopter blades with different cores

In this paper, the experimental results of structural vibratory testing for the light multipurpose helicopter main rotor blade of composite laminated materials are presented. The aim of the main rotor blade vibratory testing was to define the basic aeroelastic properties of the blade. This testing included the determination of the natural oscillation modes and natural frequency of the structure in oscillations, as well as defining the blade structural damping. The measurement was performed for three different full scale models with three different types of cores of the main rotor blade: Rohacell 71 polyurethane foam, Nomex aramid honeycomb and Nomex phenolic honeycomb. The results are presented in this paper.