Development of Random Fatigue Data for Adhesively Bonded and Weldbonded Structures Subjected to Dynamic Excitation

Prediction methods are being developed to determine the sonic fatigue life of various weldbonded and adhesively bonded aircraft structures when exposed to high intensity acoustic excitation. This paper describes the results of the experimental investigations performed by the AF Flight Dynamics Laboratory to obtain the factors that affect the random fatigue life of typical aircraft structural joint configurations. The structures tested included full-scale components, simple beam sections, and acoustic panel configurations. A variety of aluminum skin thicknesses, stiffener configurations, and bond systems have been tested under dynamic excitation. The bond systems tested begin with the weldbond systems developed in the early 1970s up to the present bond systems. Random flexural fatigue curves for two modes of failure have been developed: adhesive bond system failure and metal fatigue failure. These curves are part of the design criteria needed to predict the sonic fatigue life of weldbonded and adhesively bonded structures.