A Proposed Highly Damped Repair for the Aft Fuselage of the F/A-18
DEFENCE SCIENCE AND TECHNOLOGY ORGANISATION VICTORIA (AUSTRALIA) PLATFORM SCIENCES LAB
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Currently an increasing number of RAAF FA-18 aircraft are developing acoustic fatigue cracks on the rear fuselage. Acoustic fatigue is the result of high frequency lateral vibration of an aircraft panel as a result of time varying pressure waves caused by engine andor aerodynamic effects. While the exact broadband power spectral density PSD spectrum is not available for this area of the FA-18, the PSD is known for the inlet nacelle area in which cracking has occurred. Cracking in the inlet nacelle proceeded cracking in the aft fuselage by a period of several years. As a result the inlet nacelle experiences a more severe spectrum and is the PSD adopted here. Viscoelastic damping materials are used in this repair in conjunction with the constrained layer technique to reduce the lateral vibration. Since viscoelastic materials have a limited temperature range it has been necessary to use two types of damping materials to cover the expected temperature range. A highly damped repair is proposed for the aft fuselage area and is shown to be significantly effective in reducing the crack growth rate.
- Attack and Fighter Aircraft