Toughening effect of CB-epoxy interleaf on the interlaminar mechanical properties of CFRP laminates

Carbon black (CB) reinforced epoxy (i.e., CB-epoxy) interleaf was employed to improve the interlaminar mechanical properties of carbon fiber reinforced plastic (CFRP) laminates. Double cantilever beam tests showed that the Mode-I fracture toughness was increased with addition of CB-epoxy interleaf. With 15 g/m2 addition of CB, the CFRP laminates demonstrated the highest Mode-I fracture toughness and resistance, which were 50.3% and 88.6% higher than those of pristine CFRP laminates, respectively. End notched flexure tests demonstrated the similar toughening effect of CB-epoxy interleaf on the Mode-II fracture toughness of CFRP laminates. With 10 g/m2 addition of CB, the CFRP laminates demonstrated the highest Mode-II fracture toughness, which was 145% higher than those of pristine CFRP laminates. Fracture surfaces were observed to explore the enhancement mechanisms. Moreover, finite element analyses based on the cohesive zone model were performed, which indicated the increased interlaminar tensile and shear strengths.