Assessment of moisture absorption in marine GRP laminates with aid of nuclear magnetic resonance imaging

Abstract

The diffusion of water in an isophthalic polyester glass reinforced composite laminate, typical of marine applications, has been studied through accelerated water uptake tests involving total immersion in seawater at 40 and 60°C. Gravimetric analysis has shown that at 40°C, a Fickean type diffusion is operative with a saturation level of 0·8% whereas at 60°C, a two stage Langmuir type diffusion is operative. The nuclear magnetic resonance technique has also been used in an attempt to image the diffused water and determine its position within the composite. This has revealed that the water concentrates on the fibre/matrix interface and the concentration there is twice that of bulk of the matrix. The diffusion process appears to be aided by 'wicking' along the fibre/matrix interface.