The University of Applied Sciences Upper Austria houses a Talbot-Lau grating interferometer (TLGI) X-ray computed tomography (XCT) system (SkyScan1294, Bruker). The phase contrast XCT scanner uses a microfocus X-ray source, an 11 MP detector and three specially designed X-ray gratings to simultaneously extract information about absorption, refraction, and scattering. In contrast to conventional XCT, TLGI-XCT provides three complementary characteristics in a single scan of the specimen: a) the absorption contrast (AC), b) the differential phase contrast (DPC), and c) the dark-field contrast (DFC). The second system is called TalInt and was developed by Microworks (Germany). It is an adaptable and versalite TLGI radiograhy system tha can be fitted into exsiting XCT system.

Using these two different TLGI systems in the ImageHeadstart project, we visualize various samples including CFRP laminates that are used in lightweight applications, e.g. in combination with aluminium foam cores. The application of such multi-material lightweight sandwich panel structures can increase the structural efficiency and impact energy absorption. However, using conventional XCT it is not possible to visualize fine structures, e.g. single struts and walls in the foam, and the weaving pattern in the CFRP laminate at the same time. 

Due to the fact that DFC delivers morphological information in the sub-pixel regime depending on the local scattering power, dark field imaging delivers information that may otherwise be inaccessible using conventional XCT. Using a Talbot-Lau XCT we show that dark field images yield a high contrast and a strong signal at interfaces, in particular for the foam microstructure and the carbon fiber rovings in the CFRP panel. The specimen shown below was scanned at isometric voxel size of 22.8 μm.