Kb. Khalid et al., Multi-component mixture modeling for the dielectric properties of rubber wood at microwave frequencies, HOLZFORSCH, 53(6), 1999, pp. 662-668
Dielectric properties from 1 to 18 GHz of rubber wood are modeled using gen
eralized mixture equations and also with equations proposed by Weiner, Kras
zewski, Looyenga and Landou, Lichtenecker. Dielectric properties were measu
red with an open-ended coaxial line-sensor in three structural directions l
ongitudinal, radial and tangential and at different moisture contents. The
dielectric constants were predicted well by the Weiner model for all struct
ural grain directions and it was found that the degree of binding decreases
with increasing frequency. However, the Weiner model cannot be used for pr
edicting the dielectric loss factor at frequencies below 3 GHz. This may be
due to the high conductive loss in this frequency region. The lower value
of the exponents in generalized mixture equation was found suitable for fit
ting the experimental data as well as the Kraszewski equation. Values predi
cted by Lichtenecker equations are in well agreement with the experimental
data at higher microwave frequencies. The prediction of dielectric loss fac
tor using Kraszewski, Looyenga equations were not possible at frequencies b
elow 3 GHz since it is dominated by conductive loss. Above 3 GHz, it was we
ll predicted by Kraszewski and Looyenga equations.