X-ray tomography imaging of sandwich panels made of ramie fibre and carbon fibre

This paper uses X-ray tomography to investigate the microstructure of two novel eco-friendly bio-composites that could be used in aircraft secondary structures. One sample each of two sandwich panels are studied. The two samples both have a ramie fibre honeycomb core. One is covered with sheets made of ramie fibre and the other is covered with sheets made of carbon fibre. With the results of the scanning, this paper aims to discover the critical features which may affect the mechanical properties and multifunctional performance of the composites. The scanning consists of two steps; the first involves imaging the whole sandwich panels, and the second provides a higher resolution region of interest scan of 2*2 cm2 strips. In each step of the scanning, samples were bound together so that two sets of data could be imaged in one operation, thus time and facilities access costs were reduced. Reviewing the data and images, more defects could be found in the ramie fibre surfaced composite than the carbon fibre, which is consistent with the low failure load achieved in a mechanical pull-off test reported elsewhere. These features are related to (i) surface finishing, (ii) voids in the matrix and (iii) an uneven application of adhesive. The scans provide useful datasets that can be used to both inform improvements in the manufacturing process and give insight into the performance of the material during mechanical testing.