Wm. Banks et al., NONDESTRUCTIVE EXAMINATION OF COMPOSITE JOINT STRUCTURES - A CORRELATION OF WATER-ABSORPTION AND HIGH-FREQUENCY DIELECTRIC PROPAGATION, Journal of physics. D, Applied physics, 29(1), 1996, pp. 233-239
Applications of high-frequency dielectric measurements (300 kHz to 3 G
Hz) to the non-destructive examination (NDE) of composite structures a
re discussed. Preliminary data indicate that the method, previously us
ed for aluminium bonded structures, can be applied to bonded carbon fi
bre composite structures. Water ingress into the bond structure was ob
served to influence both the time- and the frequency-domain data. Comp
arison of exposed and dry joints demonstrated that a good correlation
exists between changes with time in the dielectric properties of the c
omposites and the extend of water uptake in the matrix. Parallel gravi
metric measurements were also performed. Diffusion of water into the c
omposite structures is discussed in terms of various models. This pape
r demonstrates that this NDE method may be used for assessment of the
water content in the matrix and has general applicability to the study
of carbon-reinforced matrix materials.