The fracture behaviors of carbon nanotube and nanoscroll reinforced silicon matrix composites

Fracture properties of both carbon nanotube (CNT) and carbon nanoscroll (CNS) reinforced silicon (Si) matrix composites under tension are investigated by molecular dynamics simulations. It is found that either a single-wall CNT or a multi-wall one (MWCNT) will be pulled out if the length of the CNT is short, while brittle fracture of CNT will happen for a relatively long one. It is interesting to find that the "sword-in-sheath" fracture mode observed experimentally in a long MWCNTreinforced alumina matrix composite is verified well by our simulations. Furthermore, comparing to a CNT reinforced Si matrix composite, fracture toughness of a CNS reinforced one can be significantly enhanced by both the length and the layer of the CNS. Crack in CNS propagates along its circumference and moves inward layer by layer so that large parts of the fracture energy are dissipated. The results provide a direct understanding of the fracture strength observed experimentally and an insight for improving the fracture toughness of some novel composites.