Hybrid effect of carbon nano-fillers on the interlaminar fracture toughness of fiber metal laminates

Interlaminar fracture failure is the dominant factor restricting the development and application of fiber metal laminates (FMLs). In the current work, the primary purpose is an assessment of the effect of the hybrid combination of graphenes (GNPs) and multiwalled carbon nanotubes (MWCNTs) on the interlaminar performance of FMLs. The effect of different ratios (GNPs: MWCNTs = 1:1, 3:7, 7:3) of hybrid carbon nano-fillers on the mode I and mode II interlaminar fracture strain energy release rates (G Iota C and G Iota Iota C) of FMLs containing GNPs and MWCNTs hybrid modified epoxy matrices are studied via double cantilever beam and end notched flexure tests. Results indicate that different ratios of GNPs and MWCNTs have different effects on the mode I and mode II interlaminar fracture performance of the samples. Compared with that of the baseline material, the G Iota C of hybrid modified FMLs with GNPs: MWCNTs = 7:3 is increased by 344%. By contrast, the G Iota Iota C of hybrid modified FMLs with GNPs: MWCNTs = 3:7 is increased by 82.9% relative to the baseline value. Scanning electron microscopy of the fracture surface reveals the synergistic toughening mechanism of the two hybrids.