ELECTRIC-FIELD FLUCTUATIONS IN RANDOM DIELECTRIC COMPOSITES

When a composite is subjected to a constant applied electric, thermal, or stress field, the associated local fields exhibit strong spatial f luctuations. In this paper, we evaluate the distribution of the local electric field (i.e., all moments of the field) for continuum (off-lat tice) models of random dielectric composites. The local electric field in the composite is calculated by solving the governing partial diffe rential equations using efficient and accurate integral equation techn iques. We consider three different two-dimensional dispersions in whic h the inclusions are either (i) circular disks, (ii) squares, or (iii) needles. Our results show that in general the probability density fun ction associated with the electric field for disks and squares exhibit s a double-peak character. Therefore, the variance or second moment of the field is inadequate in characterizing the field fluctuations in t he composite. Moreover, our results suggest that the variances for eac h phase are generally not equal to each other. In the case of a dilute concentration of needles, the probability density function isa singly peaked one, but the higher-order moments are appreciably larger for n eedles than for either disks or squares.