A One Shot Multi-Material/Polymer Differentiation with Spectral CT – first insights from the perspective of materials science

Photon counting detectors are gaining traction in material science, especially for lab-based CT. However, the possibilities that this technology enables are yet to be demonstrated for a wide variety of applications. Therefore, it is of great interest to see what multi-spectral CT imaging of polymer composite specimen is capable of and what the challenges and limitations are. To evaluate this, we scanned a 3D printed phantom containing 11 different thermoplastic, three thermosetting polymers and a variety of different filler materials such as graphene, carbon fibers and glass, as well as composites like wood and carbon fiber reinforced plastic (CFRP), using a TESCAN UniTom XL CT equipped with a spectrally resolving photon counting detector. We captured energy-resolved data between 20 and 160 keV, across 140 energy levels. By analyzing the shape and height of the polychromatic spectrum, we independently quantified the effective atomic composition Zeff and the density ρ for every voxel, which allowed us to evaluate new material characterization options. Also new challenges were identified, especially about how to deal with the large amount of image data and how to find data reduction schemes which can easily be implemented in practical workflows.