Effect of Dimensions and Agglomerations of Carbon Nanotubes on Synchronous Enhancement of Mechanical and Damping Properties of Epoxy Nanocomposites

In order to achieve simultaneous enhancement of mechanical and damping properties, epoxy resin nanocomposites reinforced with a series of carboxylic multi-walled carbon nanotubes (C-MWCNTs) with different dimensions were prepared. A solution-based high-speed shear dispersion method was developed. The dispersion mechanism of carbon nanotubes was studied, and the degree of dispersion difficulty of carbon nanotubes with different dimensions was evaluated by theoretical calculation, and the minimum size of agglomerates for dispersion based on the mechanism of rupture was deduced. Then, the effect of synchronous enhancement on the mechanical and damping properties was tested by experiment. The effects of dimensions and agglomerations on the tensile properties, damping properties, and glass transition temperature (T(g)) of the nanocomposites were investigated. The ranking of dispersion difficulty was verified using the deviations between predicted and experimental tensile modulus. The experimental results showed that the effects of synchronous enhancement on the mechanical properties and damping capacity of two kinds of specimens were remarkable and the only drawback was that their T(g) showed the maximum decrease. Further studies indicated that C-MWCNTs with large aspect ratios and large specific surface areas possessed better effects on synchronous enhancement, but caused a decrease in the glass transition temperature, while agglomeration had the opposite effect. The results of this work would be helpful for preparing improved structural damping integrated composites.