The diffusion of liquids into resins and composites

Abstract Existing methods of assessing the resistance of a polymer to environmental attack are of only limited use. A new technique, which utilizes radiolabelled diffusants, has been developed to study the diffusion of liquids into thick sections of polymer‐and glass‐fiber‐reinforced laminates. This technique allows the construction of concentration profiles of the liquid in the polymer at any time, and diffusion coefficients can be calculated from short‐term data. The application of this method of measurement has given a clear picture of the way in which water diffuses into vinyl ester resins and their glass‐reinforced laminates. The effects of stress and damage on this diffusion pattern have been quantified. It has been found that the presence of stress enhances the diffusion, and that the diffusion coefficient is further increased by the presence of a stress concentration. No evidence has been found, however, to suggest that the liquid “wicks” along the fibers when stress concentrations are absent.