Dielectric and mechanical assessment of water ingress into carbon fibre composite materials

High frequency dielectric measurements (300 kHz–3 GHz) have been used to assess the water uptake by bonded composite resin joint structures. Comparison of exposed and dry joints demonstrated that a correlation exists between changes with time in the dielectric properties of the joints and the extent of water uptake in the matrix as determined gravimetrically. Diffusion of water into the joints is discussed in terms of various models. The changes in mechanical properties as a function of water uptake are reported over an extended period of time. The use of dielectric measurements as a non-destructive examination method for the assessment of water ingress into joint structures is demonstrated.