Mode-II interlaminar fracture toughness of GFRP/Al laminates improved by surface modified VGCF interleaves

Abstract

Mode-II interlaminar fracture toughness of GFRP/Al (aluminum) laminates is improved by employing acid treatment to an Al plate and inserting surface modified vapor grown carbon fiber (S-VGCF) between the Al plate and a GFRP layer. End notched flexure (ENF) tests are carried out to investigate the effect of S-VGCF addition on the Mode-II interlaminar fracture toughness. The experimental results demonstrate that the critical load and Mode-II fracture toughness of the specimen with acid treatment of Al plate and 10 g/m2 addition of surface modified VGCF are enhanced by 135.51% and 425.16%, respectively, compared to those of corresponding pristine specimen. Due to the presence of the oxygen containing functional groups, the specimens with addition of S-VGCF possess much higher Mode-II fracture toughness compared to the specimens with addition of pristine VGCF. Laser scanning and scanning electron microscopies are employed to observe the fracture surface of specimens to reveal the improvement mechanisms. Moreover, numerical simulations are performed based on the cohesive zone model to verify the experimental results. The interfacial shear strength between the Al plate and the GFRP layer are also predicted by the numerical simulations.