Epoxy/Multi-Walled Carbon Nanotube Composites-Structure, Viscoelastic and Nanomechanical Properties

The viscoelastic, structural and nanomechanical properties of composites containing multi wall carbon nanotubes in epoxy resin at different weight fractions (0.03, 0.1, and 0.3 wt%) were evaluated by performing nanoindentation, dynamic mechanical thermal analysis (DMTA) and scanning electron microscopy. The hardness and elastic modulus were calculated from the recorded load-displacement curves. The indentation impressions were then imaged using scanning electron microscopy. The hardness and elastic modulus values as a function of multi wall carbon nanotube content for the epoxy and its composites were obtained on the basis of 70 nanoindentation tests for each sample. The results show that the addition of very low amount of nanotubes to epoxy exerts reinforcement effect on the viscoelastic and nanomechanical properties, which strongly depend on the interfacial interactions. Thus, the non-modified MWCNT reinforced samples exhibit higher hardness (similar to 7%) and insufficient change of the elastic modulus compared to the neat epoxy composites. Whereas DMTA results show about 22% improvement of the storage modulus for the 0.1 wt% amine-modified MWCNT/epoxy sample. This indicates the existence of a strong surface adhesion between amine-modified carbon nanotubes and epoxy matrix producing significant reinforcement, which affects also the composite fracture surfaces.