High-resolution nondestructive testing of ceramics and composite materials

A high ultrasound system for the frequency range of 10-200 MHz is used to detect small defects and inclusions in the order of 30 im or less in engineering ceramics. Rayleigh wave techniques are used to detect cracks and inclusions close to the surface of the ceramics. Thermal waves allow to detect defects close to the surface of ceramic components, to measure layer thicknesses or to characterise thermal resistances. Small defects and variations in the density destribution of materials are imaged by x-ray computed tomography with high contrast. In the reconstructed cross sections a pixel size or 10 Im is realized. Nuclear magnetic resonance imaging has been used to study the ageing process in prepregs. The same techniques was employed to study the content and distribution of moisture in fiber composites.