Tensile behaviour of open hole flax/epoxy composites: Influence of fibre lay-up and drilling parameters

Abstract

The present study reports on a systematic experimental test that evaluates the effect of drilling parameters on the open-hole tensile properties of flax fibre epoxy reinforced laminates. Additionally, three lay-up configurations of the flax fibre, namely, [0°/90°]₆, [0°]₆ and [±45°]₆, were investigated and compared. The results demonstrated that the [0°]₆ lay-up configuration was superior in terms of mechanical or tensile strength retention of the composites given an 8 mm hole. Conversely, damage due to delamination was not significant due to the changes in feed rate and cutting speed. This suggests that the drilling parameters were less sensitive towards the mechanical strength of the flax fibre composites with the drilled hole. The less severity of the delamination can be attributed to the high fracture toughness (high mode I critical strain energy release) of the flax fibre when compared with that of the synthetic fibre reinforced composite counterparts. The use of the step drill bit design also potentially contributes to the reduced severity of the delamination damage to the flax fibre composites.