Predicting multi-axial diffusion of water in laminated composite structural components

Abstract

This study examines the diffusion of water in fiber-reinforced polymer (FRP) laminated composites, comprising epoxy resin and unidirectional glass fibers, at different material and structural scales. Experiments on the diffusion of neat resin, FRP laminas in the axial and transverse fiber directions, FRP laminated composites with different stacking sequences, and FRP plates, rods, and pipes are conducted to obtain the diffusion processes at different length scales. Simultaneously, a diffusion model for a laminated composite is formulated to mathematically describe the multi-axial diffusion processes in FRP composites at various length scales, i.e., single lamina, laminated stacking sequence, and component. The study shows that the diffusivity constants calibrated from neat epoxy resin and unidirectional laminas are adequate to predict the diffusion responses of laminated composite systems and structural components of larger sizes. This capability is useful in predicting the long-term diffusion responses of FRP composites of complex geometries and large sizes where conducting diffusion tests on such systems is not feasible.