Dealing with missing angular sections in nanoCT reconstructions of low contrast polymeric samples employing a mechanical in situ loading stage

While in situ experiments are gaining importance for the (mechanical) assessment of metamaterials or materials with complex microstructures, imaging conditions in such experiments are often challenging. The lab-based computed tomography system Xradia 810 Ultra allows for the in situ (time lapsed) mechanical testing of samples. However, the in situ loading setup from this system limits the image acquisition angle to 140$^\circ$. For low contrast polymeric materials, this limited acquisition angle leads to regions of low information gain, thus preventing an accurate reconstruction of the data using a filtered back projection algorithm. Here we demonstrate how the information gain can be improved by selecting an appropriate position of the sample. A low contrast polymeric tetrahedral microlattice sample and a specifically structured sample, both scanned over 140$^\circ$ and 180$^\circ$, demonstrate that the missing structural details in the 140$^\circ$ reconstruction are limited to an angular wedge of about 20$^\circ$. Depending on the sample geometry and structure, applying simple strategies for the in situ experiments allows accurate reconstruction of the data. For the tetrahedral microlattice, a simple rotation of the sample by 90$^\circ$ provides enough X-ray absorption for an accurate reconstruction of the geometry.