Modified Angstrom's Method for the Measurement of Thermal Diffusivity on the Microscale within Carbon-Carbon Composite Materials

An infrared camera was used to monitor temperature evolution across the surface of carbon-carbon composite materials. One side of the sample was periodically heated using a pulsed laser. To avoid emissivity variations, infrared images were taken at 5 equilibrium temperatures between room temperature and 110 ^oC. A temperature calibration polynomial was determined for each pixel using those images. A custom program was written to determine the diffiusivity values between any two, user-selected points. The thermal diffiusivity calculation requires knowing the amplitude and phase of the "temperature waves." Due to limited data, a sine-wave fit was made to the data at each pixel to determine amplitude and phase. The results for two composite samples will be shown that are consistent with bulk sample flash thermal diffusivity measurements made on uni-directional carbon-carbon composites. Video of the temperature with position and time will also be shown for carbon composites with 0^o and 90⁰ unidirectional fiber orientation in alternated layers with two different sample orientations..