Damage characterisation of flax fibre fabric reinforced epoxy composites during low velocity impacts using high-speed imaging and Stereo Image Correlation

• Published in: Composite structures 2018-10, Vol.202, p.1186-1194
• Main Authors: Cuynet, Amélie, Scida, Daniel, Roux, Émile, Toussaint, Franck, Ayad, Rezak, Lagache, Manuel
• Format: Article
• Language: English
• Subjects: Flax fibre composites; High-speed imaging; Impact and post-impact behaviour; Mechanics; Mechanics of materials; Physics; Stereo Image Correlation (SIC)
• ISSN: 0263-8223; 1879-1085
• DOI: 10.1016/j.compstruct.2018.05.090

This work aims at studying the low velocity impact and post-impact behaviour of flax/epoxy composites. The samples were composed of 8 plies of 2/2 twill weave fabric. The experimental device used for impact tests was a drop tower with impact energies varying from 5 to 34 J (perforation). Pictures of the sample were captured during the test with two high-speed cameras in order to perform high-speed imaging and Stereo Image Correlation (SIC) analysis. Residual properties have been assessed by bending after impact tests. High-speed imaging easily detected the back face cracks at maximum deflection while some were almost invisible after impact. The results also highlighted the material’s behaviour in three-stages. At low energy, no damage was observed. The cracks and the recovered energy evolved proportionally with the impact energy between 5 and 25 J, and then reached a threshold. The post-impact tests showed that even a 5 J impact resulted in a degradation of composite performance, with a loss of approximately 10% in stiffness and 21% in strength.