Lognormal distribution - model for fatigue life and residual strength of composite materials

The differential equation of Yang for residual strength degradation in composite materials subject to fatigue loading is considered for obtaining the lognormal distribution as a model for the fatigue life of a composite material. Using this model, an ad-hoc method for estimating the physical parameters of the composite system is suggested. An example illustrates the use of our method in analyzing data. Since Yang's differential equation is for composite materials, our objective was to derive a model for composite materials. However, the methodology can be extended to other metals and materials.