Effective Thermal Conductivities of Fibrous Composites

Abstract

Most composite research to date has been concerned with mechanical properties. However, with anticipated use of composite materials in high temperature aero-space structures and other applications, thermal properties have become essential design information. This paper summarizes the results of a rigorous analysis to determine the steady-state effective thermal conductivities of fiber-matrix type of composites. A principal purpose of the present work is to investigate a class of heat conduction problems for which the proximity effects of the embedded fibers are significant. The fibers are considered dispersed uniformly in a matrix of resin. The dispersion patterns or configurations considered are: (1) uni-directional fibers in a matrix, as the simplest geometry, and (2) 0/90 configuration in which uni-directional tapes are overlaid at 90 deg to each other. The method of analysis is to solve a two-region steady-state heat conduction equation analytically or numerically. The analysis assumes prior knowledge of the geometry and the thermal conductivities of the composite constituents.

Development of Lotus-Type Porous Copper Heat Sink

“…The thermal resistance R b;i of the LCHS is calculated by the eqs. from (14) to (18). The pore diameters of the LCHS are 0.1, 0.3 and 0.5 mm under the same porosity of 0.5.…”

“…Behrens 13) investigated the effective thermal conductivities of composite materials analytically and proposed a simple equation for predicting the effective thermal conductivity. Han and Cosner 14) conducted a numerical investigation into the effective thermal conductivities of fibrous composites.…”

The inverse determination of the volume fraction of fibers in a unidirectionally reinforced composite for a given effective thermal conductivity

“…Currently there are many papers in which the effective thermal conductivity coefficient is determined for a regular arrangement of fibers for given thermal conductivity of constituents and volume fraction of fibers (the direct problem). The method of determination is usually based on the solution of the heat transfer equation at a microstructure level in repeated elements of an array [Han and Cosner 1981]. But to our knowledge no paper has considered the inverse problem of determination of the volume fraction of fibers for a given effective thermal conductivity.…”

Thermal conductivity prediction of closed-cell aluminum alloy considering micropore effect

“…Corresponding to different structure type, many empirical formulas for porous media have been proposed in the past. The successful examples include the Maxwell model fit for the dilute granule type porous media, 1 the Maxwell-Eucken model applied to matrix type, 2 and the Beherm model suitable for the fiber porous material. 3 The closed-cell metal foam belongs to a kind of granular porous media in which the void volume is occupied by gaseous components.…”