Effect of CNTs dispersion on electrical, mechanical and strain sensing properties of CNT/epoxy nanocomposites

The remarkable electrical and mechanical properties of carbon nanotubes (CNTs) render CNT-reinforced nanocomposites as potentially attractive materials for strain-sensing and monitoring purposes. The dispersion state of CNTs in polymeric matrix has a significant role on the physical and the mechanical properties of the resulting CNT reinforced nanocomposites. In this study, a series of experiments were designed to investigate the effect of dispersion process parameters and CNT concentration, as well as their interactions on electrical, mechanical and strain sensing properties of CNT/epoxy nanocomposites. Composite samples were produced under different CNT/resin dispersion conditions based on a design of experiments approach, and were characterized using tensile testing, conductivity measurements and micrography. Based on the results, two regression models were established to predict the electric conductivity and the tensile strength of the CNT/epoxy nanocomposites. The robustness and accuracy of the models were verified by implementing verification tests. It was found that the nanocomposites fabricated by dispersing of lower amount of CNT with high mixing speeds and long mixing times had improved sensory properties and were more suitable for strain sensing applications. The effect of post dispersion state on electrical conductivity was also investigated by curing nanocomposites into a magnetic field. A straight forward 2D percolation-based model was used to predict the electrical conductivity and piezo-resistivity of the magnetized nanocomposites. Both Experimental and numerical results showed that the electric conductivity could be increased significantly with post dispersing of CNTs using magnetization.