Thermal diffusivity

Thermal diffusivity is the thermal response of material derived from transient heat flow conditions. For a composite material, the values for the matrix are often used for the composite. The thermal diffusivity may be determined knowing the density and specific heat. The flash methods as in ASTM E1461-92 are for homogeneous opaque solid materials and can be used for composite materials. The flash source may be a laser, a flash lamp, or an electron beam. The specimen is typically a thin circular disc with a front surface area less than that of the flash beam. The initial temperature of the specimen is accurately controlled and a thermocouple or similar temperature measuring device attached to the rear face of the specimen or an infrared sensor measures the resulting rear face temperature rise after a thermal flash.