| Abstract [eng] |
This thesis describes a methodology involving X-ray computerised tomography (CT) for the evaluation of defects present inside the polymer composite materials. This research has been done in order to study the internal structures of polymer composites and find out the nature and distribution of any defects inside such materials. The rationale behind conducting this research has been derived from the consideration that defect and inhomogeneity properties of the composite can seriously affect the performance of the materials, and at the same time, two-dimensional observations can never give us a representative idea of the inner structure of the material. The experiment part of the research consisted of six piezocomposite samples of two types: three barium titanate (BTO) samples and three reduced graphene oxide (rGO) samples produced using various extrusion parameters. The quantitative study revealed a definite decrease in the amount of internal defects when the extrusion passes were increased. As far as the BTO samples were concerned, the total amount of pores was equal to 980 in the first sample, decreased to 74 in the second sample, and then to 8 in the third sample, while the highest quantity of pores in the first sample was in diameters of 50-100 μm and 100-200 μm. In regard to the rGO samples, the total amount of inclusions decreased from 1819 in the first sample to 314 in the second sample and further to 307 in the third sample; the most considerable decrease was registered for diameters of 25-50 μm, where inclusions reduced their number from 1061 in the first sample to 197 and then to 176, respectively.Reconstructed three-dimensional CT scans were used for the research, which made it possible to look at the samples' interior structure without cutting or harming them. This allowed for comparisons of the flaws' size ranges, geographical distribution, and morphological features in addition to their quantity. The results are significant because they show how CT-based inspection may assist determine processing parameters that result in a more uniform internal structure and enhance the assessment of composite material quality. Furthermore, the analysis made it easier to see how internal flaws are dispersed throughout the whole sample volume as opposed to only in certain cross-sectional regions. This enhances the accuracy of the data and validates CT as a useful technique for assessing the interior quality of polymer composite materials. On the whole, it was shown that the samples synthesised by extrusion at the latter conditions possessed less defect concentration and denser internal structure. As a result of investigation, it was found that the third samples were characterised by the least defect concentration and the most homogeneous internal structure among all studied samples. Therefore, it can be concluded that X-ray computed tomography can be successfully applied to three-dimensional non-destructive testing of internal defects in polymers. |
