Synergy effect of carbon nano-fillers on the fracture toughness of structural composites

The present study focuses on the development of carbon fiber reinforced polymers (CFRPs) with nano-modified matrix composed of two different carbon based nano-fillers, few layered Graphene Nano-Platelets (GNPs) and Multi-Walled Carbon Nanotubes (MWCNTs). The main purpose is to increase the interlaminar fracture toughness of CFRPs, by exploiting the synergistic effect between nano-fillers. Hybrid doped CFRPs were prepared in the first case by combining0.5%wt. GNPs and 0.5%wt. MWCNTs while in the second by 0.5%wt. GNPs and 1%wt. MWCNTs. Mode I fracture toughness (GIC) was enhanced up to 45% in the second hybrid whereas composites with GNPs or MWCNTs at equal amounts exhibited 27% and 31% increase respectively. Mode II results reported the second hybrid with the highest increase of GIIC up to 25%, while individually the same contents achieved 18% and 13% increase. Finally, Scanning Electron Microscopy confirmed the synergistic associated mechanisms of hybrids compared to the reference material.