Characterization of anisotropic moisture absorption in polymeric composites using hindered diffusion model

A new method to characterize three-dimensional, anisotropic moisture absorption in polymeric composites using experimental gravimetric absorption data is presented. This is achieved by using the three-dimensional hindered diffusion model to recover the moisture absorption properties of composites which may exhibit Fickian or non-Fickian behavior. Effectiveness of the recovery of absorption properties is assessed using artificially generated experimental data. Anisotropic diffusivities, equilibrium moisture content (M∞), and molecular binding (γ) and unbinding (β) probabilities that govern absorption dynamics are recovered by minimizing the difference between model predictions and experimental data. Using artificial moisture absorption data, diffusivities and M∞ are recovered with less than 1% error, whereas γ and β are recovered with less than 3% error in the non-Fickian diffusion case. Equilibrium moisture content is shown to be accurately determined much earlier by using partial gravimetric data obtained from the initial phases of absorption, even in the presence of considerable measurement error.