Experimental investigation of periodically excited rotating composite rotor blades

Experimental procedure for investigating the structural dynamics characteristics of thin-walled composite helicopter rotor blades undergoing periodical excitation during rotation is proposed and demonstrated. The testing setup, which is based on measurements in a vacuum chamber, provides the isolation of the structural dynamics behavior by eliminating the aerodynamic loads and introducing deliberate periodic concentrated loads at the blade's tip. The study presented in this paper includes the testing of thin-walled composite box beams in the nonrotating static case and in the case of periodic loading during rotation at various angular speeds along with comparisons with theoretical predictions. The investigation of the measured composite-related couplings and rotational effects showed some significant nonlinear characteristics. (Author)