Assessing local yield stress and fracture toughness of carbon nanotube poly(methyl methacrylate) composite by nanosectioning

A nanosectioning (cutting) method was used to test the local shear yield stress and fracture toughness (specific work of surface formation) of multiwall carbon nanotube (MWCNT) poly(methyl methacrylate) (PMMA) composites, and the effects of MWCNT content on the yield stress and toughness were investigated. The composites were prepared by a solution casting method, with MWCNT content varying from 0.05 to 1.0 wt%. Above 0.1 wt% MWCNT content, the yield stress reduced by the addition of MWCNTs. The fracture toughness of the composite was effectively enhanced by the addition of MWCNTs, ranging from 17 J/m2 for the neat PMMA to 25 J/m2 for the 1.0 wt% composite. The shear yield stresses obtained by nanosectioning were correlated to nanoindentation measurement, and possible contributions from the MWCNTs to the fracture toughness of the composite were analysed.