This document describes a method for the determination of the thermal conductivity of ceramic matrix composites with continuous fibre reinforcement. This method applies to all ceramic matrix composites with a fibre reinforcement, unidirectional (1D), bidirectional (2D), and tridirectional (xD, with 2 < x <= 3) as defined in ENV 13233, submitted to a heat flux along one principal axis of anisotropy.
The experimental conditions are such that the material behaves in an homogeneous manner for each of its axis of anisotropy and that the heat transfer occurs only by thermal conduction. The method is applicable to materials which are physically and chemically stable during the measurement.
Contrary to other methods of direct measurement which permit only to determine a value of the thermal conductivity averaged over an interval of temperature, the method described in this document, based on an adequate exploitation of the temperature record, allows to determine with a good accuracy the thermal conductivity at a defined temperature. This is more interesting since the variation of the thermal conductivity with the temperature is non-linear, which is generally the case for CMC's.
NOTE It is also possible to calculate the conductivity of CMC's by an indirect method using the following equation:
y = a x pb x Cp
where
y is the thermal conductivity;
a is the thermal diffusivity;
pb is the bulk density;
Cp is the specific heat capacity.