On the effective thermal conductivity of coated short-fiber composites

Effective-medium theories are formulated which predict the effective thermal conductivity of coated short-fiber composites. Composite aggregates that contain coated inclusions which may be aligned or randomly oriented are considered. A basic result which simplifies considerably the analysis of such systems in heat conduction problems is first established: It is shown that under certain situations a coated ellipsoidal inclusion can be replaced by an equivalent homogeneous but anisotropic one. For the composite with aligned short fibers, a microgeometry is constructed which possesses an exact solution for the effective conductivity. Self-consistent and differential schemes are formulated for the composite with randomly oriented coated short fibers.