Tension-tension fatigue tests have been undertaken on glass-fiber and carbon-fiber epoxy specimens with terminated internal plies. All specimens delaminated along the interfaces between the continuous and discontinuous plies. Delamination starts immediately, and the rate is approximately constant. Different specimens delaminate at different rates. However, when the strain-energy-release-rate amplitudes are normalized by the values for delamination under static loading, the delamination rates for all the specimens of both glass and carbon epoxy are very similar.
Terminated 0° plies are much more susceptible to delamination than ±45° plies. The number of plies terminated together has a large effect on delamination. Tapered sections with dropped plies are stronger than equivalent untapered sections with cut plies. Delamination at terminated plies can cause a significant reduction in fatigue strength, especially for carbon-fiber epoxy.