| 초록 |
Composites of an insulator matrix phase and an electrically conductive second phase show large variation of electrical resistivity with a change of composition and microstructure. Continuous contact of the second phase, so-called percolation, is one of the interesting microstructures which plays an important role in mechanical, thermal, and other properties of composites. A recent research on composites consist of carbon powder and vinyl ester resin with a detection function in fracture is interesting application of percolation phenomena in materials. The function arises from the change of percolation structure of the electrically conductive second phase, i.e., carbon powder, by an applied load. A state of percolation structure and a critical volume fraction for percolation threshold of the second phase depend on parameters concerning the morphology and the configuration of the second phase. For the optimization of microstructure and a material system in formation of the percolation structure, many experimental works on observation of microstructure and evaluation of properties in composites are necessary. In this sense, simulation is considered to be a promising method for estimation of properties and functions from design of microstructure in composites. The aim of the present work is the investigation of two-dimensional simulation to design percolation structure of the second phase with different aspect ratios. That is to clarify the relation between formation of percolation structure, the morphology and the configuration of the second phase. Finally, the results obtained from the simulation were compared with the experimental result of the carbon powder-vinyl ester resin composites in the point of percolation threshold. From the simulation prohibiting the overlap, it was predicted that a continuous path was formed at less amounts of the second phase with higher aspect ratios. In the simulation allowing the overlap, a continuous path throughout the array was formed by arranging the second phase of an aspect ratio of 5 with less than 43 % in the array.
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