Described is a sonic fatigue program to determine the effect of elevated temperature on flat integrally stiffened graphite/epoxy panels. The program involved comparative sonic fatigue testing of two J-stiffened monolithic and two bladed-stiffened orthogrid panels, with one panel of each design tested at ambient temperature and the other at 254°F. The program also involved evaluation of existing analysis methods. The elevated temperature could affect the sonic fatigue life of composite panels. The higher damping in one of the panel designs is attributed to acoustic radiation. Sonic fatigue analysis methods for multimodal nonlinear panel response need to be developed.
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J. Soovere (1985) studied this question.