Study of the fatigue behaviour of hybrid flax-glass/epoxy composites

This paper presents an experimental study of the fatigue behaviour of non-hybrid and hybrid twill flax and glass fabric-reinforced epoxy laminates. To this end, several plates of these composite materials were elaborated by the vacuum infusion process and three hybrid configurations were chosen. Specimens of these composite materials were subjected to tensile fatigue tests coupled with Acoustic Emission (AE) recording by considering two frequencies of 5 and 10 Hz with a loading level of 65%. The results from fatigue tests are deeply analysed to evaluate the fatigue loading effect on the stiffness degradation, hysteresis loops and damping ratio of the studied non-hybrid and hybrid composites. The obtained results show that the flax-glass hybridization improves the fatigue behaviour of the glass-epoxy laminate. In particular, the replacement of two internal glass layers with two flax ones reduces the loss of maximum stress by-13% and enhances the damping property by-60% at 10 Hz compared with the glass-epoxy laminate. On the other hand, the AE analysis allows identifying three classes of the recorded acoustic signals in all materials, which are attributed to the main damage mechanisms based on SEM observations.