A new data reduction method for pulse diffusivity measurements on coated samples

A new method, based on numerical solutions of the heat conduction equation, is presented for reducing flash diffusivity data to determine the diffusivity of a coating on a substrate of known thermal properties. Measurements are performed with a conventional thermal flash apparatus and the calculated curve from the numerical simulations is fitted to the measured temperature-time curve, the “thermogram”. The current work is a natural extension of previous work on single layer, homogeneous samples [1]. The main advantage of this new data reduction method, which incorporates nonlinear least-squares regression, is that both the thermal diffusivity of the coating and the thermal contact resistance can be determined. When the thermal contact resistance is small, the solution automatically converges to the perfect thermal contact case. To demonstrate its efficacy, the method is first implemented by analyzing a group of simulated data and then applied to a set of experimental data obtained from three different bilayer samples.