Cryogenic mechanical properties and failure mechanism of epoxy nanocomposites modified by multiwalled carbon nanotubes with tunable oxygen-containing groups on surface

The surface chemistry and structure of multiwalled carbon nanotube (MWCNT) plays an important role in MWCNT/epoxy nanocomposites. In this contribution, oxidized multiwalled carbon nanotube (OMCNT) with tunable oxygen-containing groups is prepared by finely controlling oxidation time and centrifugal speeds. Effects of oxygen-containing group content on mechanical properties of the OMCNT/E51 epoxy nanocomposites at 77 K are investigated in detail. It reveals that oxygen-containing groups on the OMCNT surface contribute to significant increases in tensile strength and impact resistance of the OMCNT/E51 epoxy nanocomposites compared with those of the pristine MWCNT/E51 nanocomposites. A positive correlation between the oxygen-containing group content and interfacial properties of OMCNT and epoxy matrix is demonstrated by thermogravimetric analysis and fracture morphology, and homogeneous dispersion of the OMCNT in epoxy matrix is obtained with the increase of oxygen-containing groups on surface of the OMCNT. However, proper content of oxygen-containing groups is essential to OMCNT/E51 nanocomposites because excessive oxidation tends to make sever structural defects on the OMCNT and has a side effect on cryogenic mechanical properties of OMCNT/E51 nanocomposites.