ON THERMAL CONDUCTIVITY OF COMPOSITES.
WATERVLIET ARSENAL N Y BENET R AND E LABS
Pagination or Media Count:
Thermal conductivity of composites, made of highly conductive metal fibres randomly distributed in low conductive matrices, is investigated experimentally as well as theoretically. Experimental results are presented for a factorial experiment consisting of five factors at two levels. The factors are the length of the fibre, the cross section of the fibre, the thermal conductivity of the fibre, the thermal conductivity of the matrix, and the fibre volume ratio. It is shown that the most meaningful factors to be considered for an optimum design of the type of composites in question are, in the order of importance, the conductivity of the matrix, the fibre volume ratio, and the fibre cross section. Earlier theoretical efforts consisted of mathematical models which are highly idealized, e.g. square lattices, face centered cubic models Maxwell, Rayleigh, Bruggeman. The model used in this investigation is that of a matrix filled with fibres ellipsoidal in shape and randomly distributed, according to prescribed fibre volume ratios. It is a stochastic model. An expression of the conductivity of this composite is derived and results are obtained with the aid of a high-speed computer. Theoretical prediction of the stochastic model checks with experimental data. Also it shows that additional factors are involved in describing composites which are not covered by earlier theories. These factors are fibre geometry and its distribution. Moreover, a specific specimen formulation gives a thermal conductivity similar to that of stainless steels but a density only a quarter of that of the steel. Author
- Laminates and Composite Materials