Infrared phase lock thermal wave detection method and system for thermal diffusivity of carbon fiber bundle

The invention discloses an infrared phase lock thermal wave detection method and system for thermal diffusivity of a carbon fiber bundle. The method comprises the following steps: placing a carbon fiber bundle at the central position in a vacuum drying box, vacuumizing, regulating the spatial positions of a collimating lens and an acoustic optical modulator of a laser beam, a focusing lens and the carbon fiber bundle to enable the laser beam incident angle to meet the bragg diffraction condition and to focus the laser beam on the carbon fiber bundle; carrying out sinusoidal modulation on the laser beam, and controlling the output power of an optical fiber laser by a laser power driver; and acquiring a surface thermal wave signal of a tested sample, extracting the amplitude and phase information of the thermal wave signal, and calculating the thermal diffusivity of the material according to the relationship between the amplitude as well as the phase distribution and the thermal diffusivity of the material. The system comprises the optical fiber laser, the laser power driver, the collimating lens, the acoustic optical modulator, the focusing lens, a signal generator, the vacuum drying box, a vacuum pump, a focal plane thermal infrared imager and a computer. According to the invention, the thermal diffusivity of the carbon fiber bundle is detected rapidly and accurately.