Low cycle fatigue behavior of symmetric angle-ply AS4/PEEK laminate

The present study includes low cycle fatigue behavior of graphite/PEEK composite materials. We conducted static tension tests to determine ultimate strength and low cycle fatigue tests using coupon specimens made from angle-ply laminates of which stacking sequence is [+30/-30]_4s. Stress-strain relations are measured by an extensometer during fatigue testing for every fixed cycle in order to estimate a damage accumulation. The experimental results of stress-strain relations for every fixed cycle showed an accumulation of plastic strain, so-called ratchet type strain. The tests also indicated that fatigue failure occurred when ratchet strain reached static failure strain of about 3.9%. Moreover, we point out the difference between static failure mode and fatigue one by observing failure surface.