Do thermal residual stresses contribute to the improved fracture toughness of carbon nanotube/alumina nanocomposites?

An analytical method was used to investigate the effects of thermal residual stresses on the fracture toughness of multiwalled carbon nanotube (MWCNT)/alumina nanocomposites. Computed results showed that thermal residual stresses contribute negligibly to the overall improved toughness due to immovable dislocations around MWCNTs not included, these immovable dislocations, induced by highly hydrostatic compressive stress upon MWCNTs, usually act as nanocrack nuclei and relieve stress concentration ahead of the main crack, which is evidenced by the existence of nanosteps on the fracture surface.