Development of a Strain Gauge Technique for the Measurement of the Thermal Expansion Coefficient of CC Composites as a Function of Temperature

Carbon-carbon (CC) composites have been used as high-performance materials in the aeronautical, transport, fuel and energy industries mainly due to their low specific weight, high strength, high stiffness, excellent thermal conductivity and good stability at high temperature in an inert environment. The potential use of such systems includes heat sinks and substrates of electronic components. In these applications, it is important to know the low-temperature expansion coefficient of these materials in order to match expansion characteristics with other elements. Dilatometer measurements of thermal expansion coefficient of bulk materials normally include an error caused by the expansion of the materials supporting the specimen, the contacting stress on specimen and the measuring gauges, as well as errors arising from environmental vibration. In order to obtain reliable data, a strain gauge was employed to measure the thermal expansion coefficient of unidirectional (ID) CC composites as a function of temperature. Factors influencing the accuracy of experimental results such as the type of strain gauge, adhesives and reference materials will be discussed. The thermal expansion of ID CC composites was determined over a low temperature range from 24 to 140 °C. The experiment enables temperature cycling studies to be conducted and also offers the potential to test several materials simultaneously.