A new cumulative fatigue damage model for glass fibre reinforced plastic composites under step/discrete loading

This paper presents and discusses a new fatigue damage accumulation model for Glass Fibre Reinforced Plastics under step loading. This model was formulated from a single-step constant amplitude fatigue model previously developed by the authors. Fatigue damage is defined and quantified in this paper. The model was tested using independent experimental data and predictions were found to be in excellent agreement with this data. The model was found to give a damage index closer to unity than Palmgren–Miner sum and the models proposed by Broutman and Sahu and Hashin and Rotem. The model predictions were also in excellent agreement with the two-stage fatigue data for carbon/epoxy composites [0/90, + 45 2, 0/90], suggesting that this model may be valid for composite systems other than GFRP