Nano-toughening versus micro-toughening of polymer syntactic foams

This paper examines the effect of nanoclay content on tensile and fracture properties of syntactic foam. Results showed that the tensile strength decreased slightly with increasing nanoclay content. The Young's modulus showed an increase of 17% with the addition of 2 wt% clay. Interestingly, the fracture properties reached a maximum for samples containing 1 wt% of nanoclay. SEM and OM studies were performed to scrutinize the toughening mechanisms in nanoclay-reinforced syntactic foam. A comparison of the tensile and fracture results obtained for nano-reinforced syntactic foam against short-fiber reinforced syntactic foam revealed the superiority of micro-reinforcements over nano-reinforcements in improving the tensile properties. Both short micro-fibers and nanoclay were able to give rise to substantial increase in toughness in polymer syntactic foam. Detailed comparison revealed that micro-fiber toughening was more effective than nano-toughening in this case, except for nanoclay-reinforced syntactic foam containing 1 wt% nanoclay which showed equal or even better fracture properties compared to short fiber reinforced syntactic foam. (C) 2007 Elsevier Ltd. All rights reserved.