What about the relevance of the diffusion parameters identified in the case of incomplete Fickian and non-Fickian kinetics?

The aim of this work is to study the relevance of the diffusion parameters identified on kinetics whose saturation levels are unknown. Two types of diffusion kinetics have been considered: a Fickian and a non-Fickian kinetics. Numerical experiments, based on the generation of noisy data corresponding to reference values of diffusion parameters, have been carried out. The two models used in this study are Fick's model and the «Dual-Fick» model. Identification procedures were then applied on these data sets, truncated at different critical times. In the specific case of Dual Fick kinetics, the classical least square method was compared to an alternative approach based on the piecewise analysis of the shape of the diffusion curves. The identified parameters may deviate significantly from the expected reference values when the truncation threshold of the data set precedes the steady state. Also, these inaccurate parameters impact the predictions of global water uptake, water concentration profiles and stresses gradients through the thickness of the sample.