MEASUREMENT BY FLASH METHOD OF THERMAL DIFFUSIVITY HEAT CAPACITY AND THERMAL CONDUCTIVITY IN 2-LAYER COMPOSITE SAMPLES

The well-known flash method of measuring thermal diffusivity, heat capacity, and thermal conductivity in single-layer samples has been extended to measurements in two-layer composite samples. The analysis presented allows these measurements to be made for the material in one of the layers if the corresponding values are known for the material in the second layer. An analytical solution is obtained as the basis of a computer data-reduction procedure devised for calculating the thermal diffusivity from flash-technique data. Replication of the diffusivity measurements is accomplished, in effect, by utilizing the information contained in an arbitrary number of points distributed over a wide range of the experimental temperature transient. Through the use of an empirical function closely representing the actual waveform of the heat pulse produced by a flash lamp, the measurements remain valid in thin samples for which heat losses are small. Experimentally, the method is demonstrated with data obtained for some commercial samples of bimetallic composites. © 1968 The American Institute of Physics.