Uncertainty on Fatigue Damage Accumulation for Composite Materials

The physical uncertainty on the SN-curves is due to the natural inherent uncertainty in the material and can not be reduced. The statistical uncertainty can be reduced by performing additional fatigue tests and the model uncertainty can in principle be reduced by adopting a better model. In the present paper is the physical and statistical uncertainty on SN-curves for composite material determined based on a number of constant amplitude fatigue tests performed with different mean stresses. Based on variable amplitude fatigue tests for the same material using a standard load spectrum and the estimated SN-curves based on constant amplitude fatigue tests is the model uncertainty on Miners rule determined. In most standards and regulations including [3] are fatigue design performed by using a deterministic design approach. However, calculation of the accumulated fatigue damage includes significant uncertainties for which reason a probabilistic design approach should be adopted in order to take the individual uncertainties into account in a rational manner. The stochastic models determined in the present paper forms the basis for a probabilistic modeling of the considered class of composite materials in fatigue loading. Constant amplitude fatigue tests