| الملخص | 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. |
