Modelling of fatigue microcracking kinetics in crossply composites and experimental validation

We describe a micromechanical model of transverse cracking in [alpha, 90(p)](sym) composite laminates under fatigue loading. Several features are recalled which have been the subject of another article. These concern static aspects (such as stress fields, strength distributions, etc.) and have permitted us to predict the number of cracks created during the first cycle of loading. This paper presents the principles of the fatigue model and also proposes several experimental aspects concerning the identification of parameters and validation of the model. A micromechanical hypothesis is suggested, which is based on a physical interpretation of damage to predict the reduction in residual strength of 90 degrees plies during fatigue loading. The model is incremental and allows us to describe in a simple but non-linear. way the increase of damage in the 90 degrees plies of a [alpha, 90(p)](s) laminate. We then include this fatigue aspect in our more general tool which describes a static description of the transverse cracking kinetics of a [alpha, 90(p)](sym) composite. The predictions of the simulations are validated on [0(2), 90(2)], carbon/epoxy specimens. We have observed and counted cracks during experimental tension-tension tests and compared the results with simulations. We observe good agreement between predictions of the model and experimental results. (C) 1999 Elsevier Science Ltd. All rights reserved.