In this paper, a method is introduced for impact identification in operational composite helicopter rotor blades. By applying modal impact testing to simplified fiberglass rotor blades, a frequency response function model is developed relating impact response data from the hub of a four bladed rotor to impact force data in the frequency domain. A sum of least squares method is then used to determine the most probable location of an impact force on the four blades. An analytical dynamic model is developed and solved to determine how the effects of centrifugal stiffening will affect the accuracy of the impact estimation method if a frequency response function model of the non-rotating blade is used to estimate impacts on a rotating blade. The force identification method is tested on a 15 ft diameter spin test rig. The method is shown to estimate the correct location of an impact along the chord 50% of the time while locating it correctly along the blade span 100% of the time. The force amplitude recreated in the time domain has an average error of 4.64%. Testing also shows that over time the ability to estimate the correct impact location along the chord fell slightly whereas the ability to locate the correct impact position along the blade span did not change. It is also demonstrated using the analytical model that errors in the estimated impacts due to centrifugal stiffening are lowest in the frequency ranges situated between resonant frequencies of the blade.
Impact damage detection for fiberglass composite rotor blade
Stoßschadennachweis für Rotorblätter aus Glasfaser-Verbundwerkstoff
AHS International, Annual Forum, 65 ; 928-938
2009
11 Seiten, 10 Bilder, 3 Tabellen, 11 Quellen
Aufsatz (Konferenz)
Englisch
Impact Damage Detection for Fiberglass Composite Rotor Blade
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