Development of simulation techniques for mechanical strength of nanoconposite insulating materials

Mechanical strength simulation techniques for nanocomposite resins have been developed. Coarse grained molecular dynamics are used to calculate the nanofiller distribution in resin and the stress-strain curve (S-S curve) of nanocomposite resin. A molecular orbital method based on density functional theory in which the electrical fields from a large region (um-mm) of surrounding resin are taken into consideration to obtain the inter-molecular forces for molecular dynamics. In addition, present simulations were applied to silica/epoxy nanocomposite resins and the following results were obtained. 1) While hydrophilic silica is uniformly distributed, hydrophobic silica forms a network in epoxy. These results agree with an experimental observation using scanning electron microscope. 2) The maximum level of stress of the calculated S-S curves of resin with hydrophobic silica is greater than that with hydrophilic silica. This result qualitatively agrees with the fracture-toughness measured by using a three-point bending test.