Effect of strength dispersion on fatigue life prediction of composites under two-stage loading

Abstract

Proper prediction of fatigue life is essential for safe design and operation of structures, and optimum maintenance planning. Many of the existing fatigue life models have not considered the degradation of stiffness and strength simultaneously. In this paper, a modified model is developed based on a residual stiffness and strength model. Using the proposed model, remaining fatigue life is predicted for fiber reinforced polymeric composites for two sets of experimental data under two-stage tension–tension loading. The results demonstrate that combining strength and stiffness models and considering the load sequence effect leads to the improvement of accuracy in fatigue life prediction. For better evaluation of the developed model, some existing models are compared with the present study. It is observed that, the predicted values by the proposed model are closer to experimental values in comparison with other models in most cases. To determine the variations of the predicted fatigue lives due to strength scattering, probabilistic assessment is done by Monte-Carlo simulation. This enables the designer to manage the capacity of composite structure for various design loads during the operational life of the structure.