Investigation of Hybrid Effects of CNT and Nanoclay in Tailoring Mechanical and Electrical Properties of Epoxy

Many studies performed on multifunctional properties of epoxy-based nanocomposites reinforced with CNTs and nanoclay whereas synergetic effects of CNTs and nanoclay on mechanical and piezoresistive behavior of ternary state nanocomposites still remains unaddressed. Therefore, the hybrid effects of CNTs and Montmorillonite platelets on the mechanical, electrical and piezoresistive performances of the epoxy are addressed in this study. The project was divided into two main phases. In the first phase, different CNTs morphologies (SWCNTs and DWCNTs) and weight concentrations were used. For the second phase, CNT content was kept constant while two different nanoclay loadings were used for the ternary states. In fact, the nanocomposites were prepared in two different states, i.e. the binary state, including 0.1wt.% CNTs, and the ternary states, including 0.1wt.% CNT and two levels of NC (0.5wt.% and 1wt.%). SEM, FESEM, and XRD were used for the microstructural analysis of the materials while tensile and mode I fracture tests were performed for mechanical and piezoresistive characterizations. In overall, by taking into consideration of multifunctional properties including tensile strength, fracture toughness, electrical conductivity and sensitivity, it was stated out that the ternary nanocomposites developed in phase 2 demonstrated better performance compared to the ones produced in phase 1. In fact, low tensile strength along with high variations observed in phase1, raised questions for the effective exploitation of CNTs in multifunctional properties enhancement. On the other hand, highly monotonous outcomes especially for tensile strength without sacrificing other properties indicated the effective exploitation of nanofillers in tailoring material performances in phase 2. The addition of nanoclay to CNTs doped epoxy resulted in better CNTs dispersion, hindering CNTs re agglomeration. Significant increase in critical stress intensity factor and critical strain energy release rate compared to the neat epoxy was obtained for the hybrid nanocomposites developed in phase 2 due to crack bridging and crack deflection mechanisms. The electrical conductivity of the ternary state materials increased substantially with respect to the binary nanocomposite. The hybrid nanocomposites also manifested higher piezoresistive sensitivity and a more robust signal in tensile and fracture tests, respectively