Stress-dependent Moisture Diffusion in Composite Materials

Experiments have indicated that the diffusion properties of a penetrant organic matrix composite system may change with time due to evolution of the internal mechanical strain states experienced by the constituting matrix of the composite plies. A multi-scale approach coupling the internal mechanical states, predicted by continuum medium mechanics, and their localization at the ply-constituent scale to the traditional Fick's law governing the moisture diffusion process was used in order to achieve the modeling of the response of composite laminates submitted to environmental hygroscopic loads, from the transient part of the diffusion process to its permanent stage. Various numerical practical cases were considered: the effects of the internal swelling strains on the time- and space-dependent diffusion coefficient, maximum moisture absorption capacity, moisture content, and states of internal stresses are extensively studied and discussed.