Effect of Time at Load on Fatigue Response of [(0/ ± 45/90)_s]₂ T300/5208 Graphite-Epoxy Laminate

Results of an experimental program, designed to test a time at load fatigue failure hypothesis for composites, are discussed. In order to minimize the influence of various test and material variables, testing was performed using a trapezoidal loading waveform with constant loading rates and sufficiently long hold times at load to minimize the effect of hysteresis heating. The results indicate that the fatigue life of [(0/ ±45/90)_s]₂ T300/5208 graphite-epoxy specimens can be explained by using time at load as a fatigue criterion.