Micro-mechanics of nanostructured carbon/shape memory polymer hybrid thin film

This paper investigates mechanics of hybrid shape memory polymer polystrene (PS) based nanocomposites with skeleton structures of CNFs/MWCNTs formed inside. Experimental results showed an increase of glass transition temperature (Tg) with CNF/MWCNT concentrations instead of a decrease of Tg in nanocomposites filled by spherical particles, and an increase in mechanical properties on both macro- and small mu m- scales. Compared with CNFs{,} MWCNTs showed a better mechanical enhancement for PS nanocomposite due to their uniform distribution in the nanocomposites. In nanoindentation tests using the Berkovich tips{,} indentation size effects and pile-up effects appeared obviously for the nanocomposites{,} but not for the pure PS. Experimental results revealed the enhancement mechanisms of CNFs/MWCNTs related to the secondary structures formed by nanofillers{,} including two aspects{,} i.e.{,} filler-polymer interfacial connections and geometrical factors of nanofillers. The filler-polymer interfacial connections were strongly dependent on temperature{,} thus leading the oppsite changing trend of loss tangent with nanofiller concentrations respectively at low and high temperature. The geometrical factors of nanofillers was related to testing scles{,} further leading to the appearance of pile-up effects for nanocomposites in the nanoindentation tests{,} in which the size of indents was close to the size of the nanofiller skeleton.