Sonic Fatigue Design Data for Bonded Aluminum Aircraft Structures
Final technical rept. 17 Dec 1975-20 Apr 1977
NORTHROP CORP HAWTHORNE CA AIRCRAFT DIV
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A combined analytic and experimental program was conducted to determine sonic fatigue design properties of bonded structural sections based on skin-stringer-frame design commonly applied in aircraft and to formulate data and criteria for the development of sonic fatigue resistant designs of such structure. The FM73BR127 adhesive system was used in the bonding of beam and multibay panel test specimens with 7075-T6 aluminum alloy skins and substructure. The metal surfaces that were bonded were treated with a phosphoric acid anodizing process that complied with the BAC-5555 specifications. Beam tests were conducted under narrow band shaker excitation and multibay panel tests were conducted under broadband acoustic excitation. The test results were evaluated and used in the development of a semi-empirical method for predicting sonic fatigue lives of multibay panels in acoustic environments. The range of applicability of the sonic fatigue design method is only partly determined. The sonic fatigue lives of the multibay acoustic test panels compared favorably with the lives of riveted panels of comparable size and skin thicknesses.
- Fabrication Metallurgy
- Structural Engineering and Building Technology