A cycle-by-cycle fatigue damage analysis of biaxial composite structures utilizing acoustic emission

In the present work, a fatigue damage analysis of biaxial Carbon Fibre Reinforced Polymer (CFRP) specimens loaded at two different stress levels and a fatigue ratio, R=0.1, was performed. A cycle-by-cycle approach was used, utilizing results from Acoustic Emission (AE) measurements. The aim was to investigate the influence of the applied maximum stress level on the fatigue damage accumulation process and to examine the hypothesis that damage growth occurs in a portion of a load cycle. It was found that the damage process, for the specimens loaded in lower applied stress, was gradually increased where different damage mechanisms evolved slowly towards the end of life. On the other hand, for the specimens loaded in higher applied stress, the damage process accumulated evenly and several failure mechanisms occurred in parallel at a very early stage of the fatigue life. Finally, for both loading cases, a load threshold was found, below which, there was no damage growth, supporting the hypothesis of this work.