Simulation of the Dielectric Characteristics of Syntactic Materials

Syntactic materials (spheroplastics), having a low density due to their structural features, depending on the material of the microsphere walls, may have a rather high strength and low thermal conductivity, which makes them promising as heat-insulation materials. By selecting the material of the microsphere walls and the concentration of the components of the spheroplastics, one can change significantly their dielectric characteristics. In this work, the task of modeling the effective dielectric characteristics of a syntactic material with a polymer binder and filler in the form of hollow glass microspheres is considered taking into account the presence of technological impurities in the material. A model for calculating the effective permittivity of a sample of a syntactic material is proposed based on the model of a matrix composite with several types of inhomogeneous or homogeneous inclusions. A generalized effective-field approximation for a heterogeneous medium with coated inclusions is used for the calculation. Model calculations are carried out for syntactic foam with a polydimethylsiloxane organosilicon binder and hollow microspheres with an E-glass shell, in the presence of some moisture in the material. The frequency dielectric characteristics of this material are obtained in the range of 10 2 –10 10 Hz. It is shown that an increase in the volume fraction of hollow microspheres leads to a decrease in the dielectric permittivity and dielectric-loss tangent. It is also shown that the calculated values are in satisfactory agreement with the experimental data obtained at an electromagnetic-field frequency of 9.8 GHz.