Model-based analysis and inversion of thermography data relies on knowledge of thermal diffusivities. Through-thickness diffusivity is readily measured using the flash method [1]. In composite materials, lateral diffusivities may be drastically different from the through-thickness values, but there is no comparable simple and standard approach for measuring those lateral thermal diffusivities. Welch, Heath, and Winfree [2] proposed a technique based on laser line pulse excitation, but that approach requires a reasonably powerful laser and thermal camera with the concomitant costs and safety requirements.

In this presentation, we show a simple and low cost (but not entirely nondestructive) system and method for in-plane thermal diffusivity measurement for composites. It is conceptually similar to the flash method but uses a mechanical heat source (belt sander) rather than a flash and multiple layers of the specimen are laminated together and encased in insulating foam. A thermistor measures the temperature and embedded software performs a curve-fitting (thermographic signal reconstruction) process to measure the inflection point of the temperature-time curve [3] and therefore the thermal diffusivity.

The device is built from open source hardware and software, with a materials cost well under $200 (not including the belt sander).