Effect of mechanical states on water diffusion based on the free volume theory: Numerical study of polymers and laminates used in marine application

The humid aging of composite materials is often interpreted assuming a constant diffusivity and most particularly independent on the mechanical fields. However, some experimental investigations highlight a coupling between the mechanical fields and the water diffusion in polymer based materials. In this work, this hygro-mechanical coupling is implemented through the semi-empirical free volume theory. The transient coupled problem is numerically studied using the classical finite element method. The problem is solved with the commercial code Abaqus©. Three numerical examples, emphasizing the interest of using such models in the investigation of the aging of composites, are presented. In the two first cases, the aging of pure resin specimen, under mechanical loading, is analyzed. In the last instance, the impact of the stiff reinforcements, assumed hydrophobic, on the water absorption behavior of an uni-directional laminate is studied.