Influence of low-velocity impact on residual tensile properties of nonwoven flax/epoxy composite

This paper addresses the damage resistance and post-impact damage effect on residual tensile properties of nonwoven flax fibers reinforced epoxy composites subjected to low-velocity impact. Two different impactors: hemispherical and conical, at six different impact energy levels: 4 J, 6 J, 8 J, 10 J, 12 J and 14 J were assessed. The experimental results to investigate the influence of impactor type suggest that the penetration of the impactor and induced damage are more important with a conical impactor. The post-impact damage patterns and failure mechanisms of impacted samples were characterized by ultrasonic C-scan inspection. Results suggest that damage induced by the impact included matrix cracking, and delamination, which are more important with a conical impactor. Tensile properties show a significant effect of the impact induced damage on the performance of the composite. A particular effect was identified for an impact energy from 8 J, where the tensile modulus E0 and E1 are decreased by 53.5% and 59.3%, respectively. This effect was also confirmed by the examination of the strain map, describing the deformation behavior of the material at different impact energy, where a stress concentration localized in the impacted zones was identified.