Detecting damage in non-uniform beamsusing the dereverberated transfer function response

Abstract

Delamination damage in composite rotorcraft flexbeams caused byexcessive vibratory and fatigue loads can lead to degradation in flapwise andlagwise performance of the rotor blade. In addition, delaminations can resultin rapid fatigue failure of these tailored composite elements leading tocatastrophic results. A novel damage detection strategy is evaluated in thiswork which attempts to exploit the dereverberated transfer function responseof beams with tapered geometries. This approach avoids high fidelity finiteelement models of damaged one-dimensional beams with non-uniform geometries.To obtain the dereverberated transfer function response, a virtual controlforce is applied to the reverberated transfer function response to removeresonant and anti-resonant dynamics associated with the beam's boundaryconditions. Magnitude and phase characteristics between each actuator andsensor can then be used to infer changing structural properties. Analyticaland experimental results suggest that this approach can be used toquantitatively and qualitatively infer delamination damage in non-uniformbeams. Experimental results are displayed for beams with varying thickness andwidth tapers.