A novel estimation method for fitting fatigue data in the composite wearout model

S-N curves are used in the design of composite structures to estimate their fatigue behaviour. In this work, an empirical fatigue model has been developed based on one first proposed by Sendeckyj. To reduce the complexity of the nonlinear optimization in the Sendeckyj wearout model, a new constraint is derived based on the material S-N fatigue curve and a mathematical curve fitting. To improve the Sendeckyj model's accuracy in all fatigue regions, a novel estimation method is used. In this method, an exponential model is used to determine the Sendeckyj model parameter for the low cycle fatigue region and a power-law model is used to determine the Sendeckyj model parameter for the high cycle fatigue region. The new model was compared against the original Sendeckyj model for glass fibre laminates with various polymer resins. The novel wearout method leads to more accurate parameters and more accurate S-N curve.