Abstract

Flexbeams in hingeless rotors have non-uniform geometries to form virtual hinges for the lead-lag and flap motions of blades. For bearingless rotors, the flexbeams also contain a virtual hinge for the pitch of the blades. Commonly, flexbeams are damaged through high cyclic and vibratory loadings. Damage in the form of delamination for composite beams degrade performance and can potentially cause catastrophic failure. In a beam of uniform cross section, the transverse dynamics of a beam can be characterized by four wavetypes. By tracking the progression of the waves along the beam and back again, the wavetypes can be used to infer damage. While this process has worked well for uniform beams with cracks, tapered beams are difficult to model. To avoid high fidelity spectral finite element modeling of tapered flexbeams, this paper introduces a concept involving the use of the dereverberated transfer function response to infer delamination damage. A “virtual control” is introduced to obtain the dereverberated transfer function with and without damage. Analytical and experimental results suggest that this approach can be used to qualitatively infer damage in flexbeams with tapered geometries. Preliminary experimental results are displayed for flexbeams with varying thickness and width tapers.

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