Toughening of Epoxy Nanocomposites: Nano and Hybrid Effects

Abstract

In this paper, we review recent progress made in the field of epoxy-based binary and ternary nanocomposites containing three-, two-, and one-dimensional (i.e., 3D-, 2D-, and 1D) nano-size fillers with a special focus on their fracture behaviors. Despite investigations conducted so far to evaluate the crack-resistance of epoxy nanocomposites and attempts made to clarify the controlling toughening mechanisms of these materials, some questions remain unsolved. It is shown that silica nanoparticles can be as effective as rubber particles in improving the fracture toughness/energy; but incorporation of carbon nanotubes (CNTs) or clay platelets in epoxy matrices delays crack growth only modestly. The “nano” effects of silica (<25 vol.%) and rubber (>10 wt.%) nanoparticles in toughening epoxy resin are confirmed by comparison with silica and rubber micro-particles of the same loading. There is clear evidence of both synergistic and additive toughening effects in the silica/rubber/epoxy ternary nanocomposites. In addition, positive hybrid toughening effect has been observed in the nano-rubber/CNT/epoxy composites; however, a negative hybrid effect is predominant in nano-clay/nano-rubber/epoxy ternary nano-composites. Future research directions for epoxy-based nanocomposites towards multi-functional applications are discussed.

Keywords:

• fracture
• toughening mechanisms
• binary/ternary nanocomposite
• epoxy
• interface

Funding

BM and YWM would like to thank the Australian Research Council for the financial support of this project (DP0877080; DP120104648).

Notes

* Fracture toughness K_C is the resistance of a material against growth of pre-existing cracks or flaws. It is related to the fracture energy G_C by K= (E.G_C)^0.5 where E* = E for plane stress and E/(1-ν²) for plane strain; E is Young modulus and ν is Poisson ratio. See ASTM D5045.