Flightworthy Graphite Fiber Reinforced Composite Aircraft Primary Structural Assemblies. Volume II. Tasks 6 through 12. Supplement.

Abstract : A graphite-epoxy horizontal stabilizer designed and fabricated for the F-5A fighter has been fatigue tested for an equivalent of 16,000 flight hours with no detectable damage. The stabilizer was designed to be flightworthy in every respect and to be fully interchangeable with an existing all metal F-5A stabilizer. It was loaded under spectrum load blocks, each block representing 400 flight hours comprising 30 different load levels. The testing was halted after 40 load blocks were completed, representing 16,000 flight hours or four times the design life of the aircraft. At the conclusion of the test as well as throughout the test, the stabilizer exhibited no degradation or damage from fatigue loading. Since it was very desirable to induce a fatigue failure, testing was resumed at limit load. The stabilizer was fatigue tested an additional 10,932 cycles before failure. Visual inspection revealed a single delamination of the upper surface composite skin at the inboard edge directly over the steel spar. This report contains a description of the fatigue test (set-up, loading, instrumentation, etc.) and a summary of the pertinent results. (Author, modified-PL)