Static and Fatigue Test Loading Development for an F-111 Bonded Composite Repair Substantiation.
DEFENCE SCIENCE AND TECHNOLOGY ORGANIZATION CANBERRA (AUSTRALIA)
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Substantiation of a bonded composite repair to an F-111 lower wing skin required the development of representative loads for specimen testing. This report describes the development of representative static and fatigue spectrum loads to be applied during the testing. The spectrum was based on a known representative Wing Pivot Bending Moment spectrum. Full scale static wing testing and the manufacturers original stress analysis reports were used to convert this spectrum to be representative of the stress at the region of interest in the outboard section of the lower wing skin. The spectrum representing 199 flights or 499.1 flying hours was expressed in both blocked and cycle by cycle form. Truncation was performed to reduce the total number of cycles to a manageable level and this was evaluated both analytically for the blocked spectrum and experimentally for the cycle by cycle spectrum to ensure that damaging cycles were retained. The blocked spectrum was found to give highly conservative results and this approach is recommended only where no further information about the cycle history is known. The implications of the present results for realistic spectrum truncation are briefly discussed.
- Laminates and Composite Materials