Method for studying the porosity of fluid phase samples by X-ray computed tomography under uniaxial compression

The development of composite materials and products with a complex internal structure poses questions to develop experimental methods to determine the stress-strain state. Standard experimental methods do not provide a broad picture of the internal changes in the inhomogeneous samples under loading. Moreover, a presence of internal defects, porosity, local buckling can significantly effect on the obtained results. Despite the development of tomography and data processing methods most studies are performed without any external loading on sample. The research presents a methods for studying the porosity of samples under uniaxial compression using an X-ray computed tomography. For this purpose, special equipment that allows loading the sample inside the tomography was made. Additionally, a methodology was developed. The equipment allows not only to transfer the axial compression force, but also to measure the corresponding load value. The equipment was designed to reduce artifactual rays in a place where studied sample mounted. To determine the reference points under loading, a contrasting copper grid was used. A modified Harris detector was used to quantify the displacements. The displacements of the reference points were interpolated to a regular initial grid to estimate the displacements inside the sample. Test samples were designed and manufactured using additive technologies to illustrate the methodology. A series of loadings and tomography scans were carried out for each sample. The tomography data were processed according to the methodology. As a result, the displacement fields of the samples, the values of porosity, volumetric strain and their distribution over the sample for each loading step were obtained.