Nano-/micron-scale synergistic toughening of carbon fiber/epoxy composites via interleaving co-polyimide film

Carbon fiber/epoxy composites (CF/EP) are significant components of engineering materials in defense, aerospace and transportation field. Nevertheless, one of the main obstacles to improve mechanical strength of CF/EP is delamination. In this study, a kind of hydroxyl-functionalized block co-polyimide (BOH) filming as interleaves achieved multi-scale synergistic toughening, including reaction-induced phase separation structures at nano-scale and plastic deformation of BOH enrichment at micro-scale, which aims to improve the interlaminar fracture toughness of CF/EP composites effectively. As a result, mode I interlaminar toughness at initial (G IC-NL ) and at propagation (G IC-Prop ) of CF/EP laminates interleaved with 7 μm BOH film (CF-EP/BOH7) are increased by 126 % and 183 %, respectively. CF-EP/BOH7 laminates exhibit improvement of 206 % in mode II interlaminar toughness. This multi-scale toughening method initiates a new way for improving the interlaminar toughness of CF/EP composites.