Mechanical Performance Evaluation of Carbon Nanotube Reinforced Polymer Nanocomposites at above Ambient Temperature Environments

Abstract

Present work has been focused to evaluate the mechanical performance of CNT/epoxy nanocomposites under different above-ambient temperature environments. Nanocomposites were fabricated with epoxy as a matrix materials and multi-walled carbon nanotube (MWCNT) as a reinforcement with different loadings (i.e. 0.1, 0.2 and 0.3 wt %). Mechanical properties of all these nanocomposites were evaluated by flexural testing at different elevated temperatures (30 °C, 50°C 70°C and 90 °C). Room temperature flexural test results revealed that both strength and modulus keep on increasing upto a CNT loading of 0.2%, after which the strength decreases upon further addition of CNTs whereas the modulus remains mostly unaffected. With increase in testing temperature, degradation in both strength and modulus was noticed, but the rate of this degradation was found to be significantly higher for all the nanocomposites than neat epoxy. Consequently, after certain temperature, the nanocomposite shows a poor strength and modulus than the control epoxy. This poor performance of nanocomposites at 70 °C and 90 °C temperatures can be attributed to the failure of CNT/epoxy interface due to differential expansion of epoxy and CNT. Researchers around the globe have also reported that the functionalization of CNTs further improve the mechanical properties of polymer nanocomposites. This work also reports the effect of CNT functionalization on the elevated temperature durability of the resulting nanocomposite. At 50 °C and 70 °C temperatures both the strength and modulus of functionalized CNT/epoxy nanocomposites were found to be higher than pristine CNT/epoxy nanocomposite. The DMTA analysis was also carried out for the understanding of viscoelastic properties of all the nanocomposites in the temperature range of 40 °C to 200 °C. To study the failure mechanisms, the fracture surfaces of the nanocomposites were analysed under field emission scanning electron microscope.