Characterisation of fiber lay-up and defects in CFRP using Talbot-Lau grating interferometry

Abstract

Using Talbot-Lau grating interferometer X-ray computed tomography (TLGI-XCT) we determine the fiber lay-up and quantify defects in loaded carbon fibre-reinforced polymer samples in three dimensions. In contrast to conventional XCT, TLGI-XCT provides three complementary image characteristics during image acquisition: a) attenuation contrast (AC), b) differential phase contrast (DPC), and c) dark-field contrast (DFC). Using a desktop TLGI-XCT system (Skyscan 1294), we visualize fibre bundles, resin rich areas, and defects (cracks and pores) in CFRP laminates that were subjected to low impact energies up to 15 Joules. The combined application of AC, DFC, and DPC volume data facilitates the intuitive visualization of fiber lay-up and the component´s microstructure, including resin-rich areas. Moreover, dark-field images yield a high contrast and a strong signal at interfaces improving the detection of microcracks in relatively large samples whereas these defects are barely detectable using standard XCT.