Synergistic effects of halloysite and carbon nanotubes (HNTs + CNTs) on the mechanical properties of epoxy nanocomposites

Abstract

The synergistic effects of halloysite nanotubes (HNTs) and carbon nanotubes (CNTs) on the mechanical properties of epoxy nanocomposites were investigated. The addition of hybrid nanofillers (0.5 wt% HNTs–0.5 wt% CNTs) has significantly increased the storage modulus, flexural strength, tensile strength, fracture toughness (K1C), critical strain energy release rate (G1C), and microhardness of the nanocomposites. The tensile strength and Young’s modulus increased up to approximately 45% and 49%, respectively. The flexural strength and modulus increased up to approximately 46% and 17%, respectively. K1C, G1C, and microhardness recorded improvements of up to approximately 125%, 134%, and 11%, respectively. The formation of a large number of microcracks (emanated radially) and the increase in fracture surface area (due to crack deflection) were the major toughening mechanisms in the hybrid nanocomposites. SEM images revealed that the hybrid nanofillers were uniformly dispersed in the epoxy matrix and the fracture surface was coarser than that of neat epoxy, suggesting a semi-ductile fracture. This study has shown that the synergistic effects of HNTs–CNTs hybrid nanocomposites at low content (0.5 wt% HNTs–0.5 wt% CNTs) have significantly enhanced the mechanical properties of epoxy nanocomposites.