Multiscale investigations into the fracture toughness of SiC/graphene composites: Atomistic simulations and crack-bridging model

Experiments showed that the fracture toughness of silicon carbide (SiC) ceramics can be enhanced by adding graphene-based fillers. To understand the toughening mechanism and thoroughly explore the toughening potential, we used a multiscale approach combined with molecular dynamics (MD) simulations to theoretically study the correlation between the toughening effect and the microstructure parameters of SiC/graphene lamellar composite. MD simulations demonstrated that the pull-out force can fluctuate periodically around a constant during the pull-out process and it will drop quickly to zero when the graphene sheet is pulled out from the SiC matrix entirely. The modified crack-bridging model revealed that the toughening enhancement of graphene/SiC composites can be improved with larger graphene size and volume fraction. The macroscopic fracture toughness and the atomistic level pull-out force are linked by the proposed multiscale crack-bridging model. We also found that the fewer-layer graphene sheets can better reinforce the fracture toughness than the more layer ones. These understandings may help the design and preparation of SiC/graphene lamellar composites toward better fracture toughness.