Damage investigation of cross-ply flax/epoxy composite under impact fatigue

This paper aims at studying the damage evolution of a [0/90](3S) cross-ply flax/epoxy laminate repeatedly impacted at three energy levels of 5, 6 and 7 J. Several specimen plates were prepared by the vacuum infusion technique and then subjected to repeated low-velocity impacts. To assess external damage mechanisms in the impacted plates, an inspection of the back and front faces damage was conducted by using a high-resolution digital reflex camera. Moreover, different techniques were used to evaluate the internal damage such as intensive light exposure, infrared thermal imaging, and computed X-ray tomography. The obtained results show that damage is visible even at low energy level and starts to appear from the first impacts, especially in the back face of the flax/epoxy samples. In addition, after front and back faces cracks appear, delamination is the most predominant damage mechanism that occurs during the different phases of impact fatigue loading. Its size is found to extend with the energy level and the multiplication of impacts.