Influence of Fiber Orientation and Aspect Ratio on the Effective Conductivity of Parallelepipedonal-Cell Short-Fiber Composites

Modern applications of short-fiber composite materials demand accurate characterization of their macroscopic thermal properties. Many physical and microstructural factors influence the effective thermal conductivity of a composite material body. The objective of the current work is to investigate the influence of the microstructure configuration on the effective conductivity of a parallelepipedonal-cell composite containing equal-sized short fibers; the orientation and aspect ratio of the fibers are varied. The possible presence of voids in the matrix or of an interfacial thermal resistance between the constituent phases are not considered. A previous continuous formulation and computational implementation of heat conduction in a statistically homogeneous and periodic composite material are employed. The approach is based on the application of homogenization theory to the variational form of the original heat conduction boundary value problem for the multiscale composite medium. The variational form is well suited for subsequent numerical solution by the finite element method. The expression for the composite effective conductivity is here computed for several parallelepipedonal-cell microstructures. The numerical results are critically compared with available experimental data for short-fiber composites, and indications for important future research efforts are drawn.