A concentration-dependent diffusion coefficient model for water sorption in composite

International audience; The phenomenon of diffusion coefficients depending on concentration has been observed and studied experimentally for many years. This is particularly the case for the inter-diffusion in metals [1] but has also been observed on various polymeric systems [2]. This study presents a concentration-dependent diffusion coefficient model for water sorption in a polymer matrix composite. It has been developed by studying the water uptake of a polyphthalamide short glass fiber reinforced material. According to experimental data, we postulate that the diffusion coefficient follows a modified Arrhenius equation with a concentration dependence of the pre-exponential factor but also of the activation energy. This choice is related to the evolution of the glass transition temperature during sorption, which has a profound influence on transport properties. The coupled partial differential equation of the model is solved for some applied examples by using an easy-to-implement finite difference scheme.