Abstract
An integrated accelerated testing method (Integrated ATM) has been proposed by the authors as a method for evaluating the strength and durability of CFRP and its structures. The strength scatter in the Integrated ATM formulation is expressed by a Weibull distribution, and its shape parameter is independent of the type of load (static, creep, or fatigue) and the environment (time or temperature). Christensen's viscoelastic crack kinetics law, the scientific basis for the Integrated ATM formulation, covers static and creep strength but not fatigue strength. In this study, we used resin-impregnated CFRP strands as unidirectional CFRP and performed numerous fatigue tests at various stress levels to compare the scatter in fatigue strength with the scatter in static strength. The Weibull distributions for both strengths were found to be nearly identical, demonstrating experimentally that the Integrated ATM formulation can be extended to the fatigue strength of unidirectional CFRP. Furthermore, we clarified the characteristics of the scatter in the S-N curve, which shows the relationship between fatigue strength and number of cycles to failure for unidirectional CFRP.
