Fibre composite fatigue-life determination

A methodology is described for the statistical characterization of fibre composite fatigue-life data. The approach determines the most appropriate probability distribution function and then estimates the associated descriptive parameters. The methodology includes the determination of the most accurate minimum-life estimation method. Two sets of carbon fibre composite fatigue-life data are found to be best characterized by Weibull distributions, from which minimum lives may be estimated. The results of this study highlight a large difference between estimated median and minimum fatigue lives of composite materials. One set of the samples exhibited a median life of 37 022 cycles and a minimum life of 0 cycles, and the other a median life of 85 250 cycles and a minimum life of 16 000 cycles. It is concluded that minimum-life S-N plots are more appropriate for use in design engineering activities than S-N plots based, in the conventional way, on median lives.