Interlaminar fracture toughness of flax, carbon, and hybrid flax carbon‐woven fiber‐reinforced composites

Abstract The effect of the asymmetric distribution of woven flax fiber on the interlaminar fracture toughness of carbon fiber‐reinforced polymer (CFRP) is investigated experimentally via a double cantilever beam test, and the results are backed by analytical and numerical analysis. Four hybrid configurations are fabricated with different stacking sequences of (CFRP) and flax fiber‐reinforced polymer (FFRP) plies. The results of hybrid specimens are compared with those of all CFRP and all FFRP specimens. The hybrid composite with one carbon/flax fiber layer at the interface requires the highest critical energy release rate, G_C, to initiate cracks. A resin layer on top of the flax plies and a carbon fiber imprint in that layer are observed, thus signifying an increase in G_C for the hybrid composites with dissimilar interface layers. Varying the number of carbon/flax fiber layers at the interface adversely affects G_C. Mode II contribution to the G_C was verified analytically for asymmetric hybrid configurations. The agreement between experimental, numerical, and analytical results is excellent. The hybridization of flax with carbon enhances the fracture toughness of CFRP while providing an opportunity to achieve lightweight, high‐performance, and eco‐friendly structures. Highlights Flax fiber is used to increase the fracture toughness (G_C) of CFRP Asymmetric carbon/flax fiber hybrid composites are designed for this purpose One interface carbon/flax hybrid exhibits a 70% increase in G_C Blocking the plies together results in reduced G_C and mode‐II fracture as well Numerical and analytical analysis agrees well with experimental results