The hydration properties of several carbon fibre composites were studied, using non-invasive MR-Micro Imaging as well as NMR- Spectroscopy, relaxation and diffusion measurements, which represents a molecular level of the study of the molecular properties of water molecules within carbon fibre composites. We have obtained 2 and 3 dimensional images of the water distribution in several uni-directional, bi-directional CFCs, as well as the hydration properties of resins of different types for production.
For the first time we were able to get MR-images of dry and hydrated CFCs. Because these materials are conductive, there is an induced current (RF field) if the sample is studied with Radio frequencies used in MR. This produces strong distortions of the images. We were able to compensate for those artefacts using special imaging coils (IBMT-production, and home built probe holder) and a certain orientation of the materials studied, with respect to the coils RF-field orientation(s).
In general we can conclude that a low but non-negligible amount of water penetrates the CFCs materials (and the resins) and forms detectable clusters of "water rich" regions. Thinking in long terms using those materials in aircraft and ship construction, we have to consider drastically changes in temperature and moisture (e.g. condensation of water) for aircraft that might slowly weaken the materials properties. Especially, in the case of strong heat and/or ice formation, those water clusters might become starting points for material defects.
This project shows ways, how to select the best material and how the final finishing of the materials (e.g. sealing) could be done.