On the cumulative fatigue damage in short carbon fiber reinforced poly-ether-ether-ketone

The actual load for mechanical structures is not always a constant stress amplitude. Therefore, in order to predict the fatigue life under various stress amplitudes, it is important to investigate whether Miner's rule is applicable or not. In this paper, rotating-bending fatigue tests under two-step loading for short carbon fiber reinforced poly-ether-ether-ketone, CFRPEEK, were carried out in order to investigate the applicability of Miner's rule. Our results indicate that the fatigue process should be divided into two stages, when referring to short fiber reinforced composites: (1) where the fatigue damage concentrates near the short fiber's end, and, (2) where it concentrates near the fatigue crack's tip. The following results were obtained; in the case of the short fiber reinforced composites, Miner's rule should be applied to each of the above-mentioned stages. Then Miner's rule is available with some scatter under two-step loading in CFRPEEK.