Fatigue response of CFRP subjected to hygroscopic ageing

The purpose of this publication is to analyse the hygroscopic ageing effects of a CFRP material subjected to fatigue. The tested material is provided by the company RiBa Composites. Because of the lack of data about fatigue in composites, there is not a specific test approved by any regulation for this analysis. Therefore, the tests are inspired by the ASTM D2344/D2344M, which is the test characterizing the short-beam strength and the moisture absorption of CFRP aged in deionized water. The difference, other than the type of applied load (the original test is performed by using quasi-static loading condition, meanwhile the fatigue test is performed by using CA loading), is in the number of specimens used. In fact, because of the long time spent by specimens to fail under low amplitude loadings, the use of five specimens per loading level for each ageing period is restricted to three specimens. Moreover, because of the definition of fatigue, for some ageing case more specimens are used and, sometimes, even different loading levels are considered. The final outcome is the analysis of the fatigue life. During the data analysis has been observed that even for CFRP materials can be made some fatigue life prediction by the use of the well know Wohloer diagram. Moreover, coefficients for the Basquin’s law have been obtained for all the ageing periods.