Enhanced tensile strength, fracture toughness and piezoresistive performances of CNT based epoxy nanocomposites using toroidal stirring assisted ultra-sonication

The importance of proper CNT dispersion is still the main challenge in CNTs doped epoxy nanocomposites. Therefore, this study was aimed to investigate the effect of toroidal stirring-assisted sonication on final mechanical, electrical and electromechanical properties of the nanocomposites. Two different samples were produced i.e. one with just sonication (M1 batch) and the other was produced using a combination of sonication and high toroidal stirring in an iterative approach (M2 batch). While piezoresistivity performance of the CNT based nanocomposites were mainly investigated in the literature for tensile mode and less attempts were conducted in presence of a pre-crack, both tensile and fracture tests were performed in this study to measure mechanical and electromechanical properties of the nanocomposites. SEM and FESEM were used for the microstructural characterizations. Results showed that M2 batch resulted in a better mechanical, electrical, and piezoresistivity performance than the M1 batch resulting from a better CNT dispersion and less amount of voids in the former compared to the latter. In fact, tensile strength and fracture toughness was increased by 70% and 17%, respectively for M2 batch with respect to M1 batch. Moreover, piezoresistive-sensitivity of the M2 batch increased 14%, compared to M1 batch. Finally, different trends in piezoresistivity was revealed in the fracture test before the occurrence of macroscopic damage, attributed to state of CNT dispersion and manifesting as a negative and positive trend for the M2 and M1 batches, respectively.