Diffusion With Time-Varying Diffusivity, With Application to Moisture-Sorption in Composites

Abstract

This paper concerns the diffusion equation when the diffusion co efficient varies with time. It has been agreed that the sorption of moisture in composites is described by the diffusion equation and that the diffusion coefficient is highly sensitive to temperature. When the temperature varies with time, as during a "thermal spike", the diffusion coefficient becomes time dependent. It is shown in this paper that the above time-variation can be treated simply and efficiently with the aid of a simple transformation. This trans formation permits the utilization of all the available solutions, that were based on a time-independent diffusion coefficient, upon a simple and easy adjustment in the time-scale.