NDTnet 1998 Aug, Vol.3 No.8

Abstract

X-ray topography is characterized by the spatially resolved detection of scattering of a sample. It combines both the advantages of radiographic imaging and the analytical information revealed by x-ray scattering, which is mainly used in crystallography. The topographic methods to investigate the structural features of non-metallic compounds by use of Wide Angle X-ray Scattering and X-ray Refractography will be presented.

X-ray refractography is an unconventional x-ray small angle scattering technique which has been developed and applied to meet the actual demand for improved nondestructive characterization of high performance composites, ceramics and other low density materials and components. It determines the amount of inner surfaces and interfaces of nanometer dimensions due to the short x-ray wavelength of approx. 0.1 nm. The mean pore size of ceramics and crack density development in composites is measured without destroying the structure by cutting or polishing for microscopy techniques.

X-ray refraction (scanning) topography visualizes the projection of the fibre nanometer debonding at spatial resolution of 20 µm. It performs an additional sensitivity to fibre orientation and has turned out to be an effective tool for determining interfaces in composites. Mean values of the fraction of debonded fibres are measured to 1% precision within a second. This is much more precise and faster than any mechanical testing could be, a desirable situation when processing is to be optimised or delicate components have to be evaluated.

Scanning a sample in the x-ray beam and detecting the deflected intensities for each position under a fixed angle of typically one minute of arc provides the data for a twodimensional computer image of the inner surface distribution. The high scattering intensities provide the possibility of high scanning speed and imaging within several minutes. Examples of analytical investigations and nondestructive evaluation will be presented. Applications to various heterogeneous materials including CMC, injection moulding composites, impact damage at and ageing of aircraft composites reveal quantitative correlation to mechanical behaviour.Applications of Wide Angle Scanning Topography will be described to visualise spatially resolved fibre and matrix orientation and degree of orientation in carbon fibre composites using advanced signal processing techniques.

Abstract Source:
Book of Abstracts, 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN: 87-986898-0-00

Full-Text Source:
Proceedings of the 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN:

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