Spectrum fatigue loading of composite bolted joints—small cycle elimination

In order to reduce time and cost of spectrum-fatigue testing it is necessary to eliminate load cycles from the load spectra. Bolted joints made of carbon fiber/epoxy composites were spectrum-fatigue loaded with a wing spectrum and specially designed spectra. It was found that low-amplitude load cycles, which are below a fatigue threshold, might not affect the fatigue life at all. Load cycles with a 50% range of the over all range of a spectrum will reduce the fatigue life slightly. But, since there are few of those load cycles for each large amplitude load cycle, all load cycles with a range less than 50% of the over all range a spectrum can be eliminated from a realistic spectrum.