Life extension of F/A 18 intake nacelle using add-on dampers

Acoustic fatigue is due to very high intensity excitation as a result of pressure waves caused by either engine/or aerodynamic effects. Currently a large portion of the F/A-18 fleet has suffered from acoustic fatigue cracking in skin panel on the lower external surface of the inlet nacelle. There has been a long history of cracking in this region, which is attributed to fatigue caused by acoustic excitation of the panel during the operation of the aircraft. Efforts to alleviate these fatigue crack growth with traditional boron/epoxy patches was not successful. This paper seek to select a set of damping material suitable for the reinforcement/damping treatment to alleviate the acoustic fatigue damage of the nacelle panel of the F/A-18 aircraft. This experimental study will address the relevance of constrained layer damping reducing the incidence of acoustic fatigue problems in the nacelle region.