Use of segmented constrained layer damping treatment for improvedhelicopter aeromechanical stability

Abstract

The use of a special type of smart material, known as segmentedconstrained layer (SCL) damping, is investigated for improved rotoraeromechanical stability. The rotor blade load-carrying member is modeledusing a composite box beam with arbitrary wall thickness. The SCLs arebonded to the upper and lower surfaces of the box beam to provide passivedamping. A finite-element model based on a hybrid displacement theory isused to accurately capture the transverse shear effects in the compositeprimary structure and the viscoelastic and the piezoelectric layers withinthe SCL. Detailed numerical studies are presented to assess the influenceof the number of actuators and their locations for improved aeromechanicalstability. Ground and air resonance analysis models are implemented in therotor blade built around the composite box beam with segmented SCLs. Aclassic ground resonance model and an air resonance model are used in therotor-body coupled stability analysis. The Pitt dynamic inflow model isused in the air resonance analysis under hover condition. Results indicatethat the surface bonded SCLs significantly increase rotor lead-lagregressive modal damping in the coupled rotor-body system.