Localized elastic modulus distribution of nanoclay/epoxy composites by using nanoindentation

The enhancement of mechanical properties by the use of nanoclay platelets in epoxy resin has been extensively investigated through numerous experimental techniques recently. Elastic modulus was obtained mainly from the tensile test of bone-like nanoclay/epoxy specimens. The results from the tensile test have only showed the globalized mechanical properties of composites and their localized elastic modulus distribution has been neglected. Despite the orientation and the degree of exfoliation of nanoclay platelets inside nanoclay/epoxy composites, the localized elastic modulus is important for the understanding of the distribution of agglomerations of nanoclay platelets. The elastic modulus of nanoclay/epoxy composite samples made under different sonication temperatures would be examined by nanoindentation to compare their localized mechanical behaviors. Scanning electron microscopy (SEM) would also be employed to study the distribution of the nanoclay clusters throughout the composites. The results showed that the elastic modulus varied throughout the composites and the nucleation theory of clusters was modified to explain the behavior of nanoclay agglomerations under different sonication temperatures in which the viscosity of the epoxy resin was varied. The gravitational effect was significant to cause the non-uniform distributions of nanoclay clusters at low sonication temperature. (C) 2006 Elsevier Ltd. All rights reserved.