In advanced ceramics, improving toughness usually relies on the introduction of a soft phase, mainly a metallic or polymeric ductile phase, which leads to a decrease on the mechanical behavior of the resulting material. Although natural materials that are strong, stiff and tough succeed due to a combination of mechanisms operating at different scales, the relevant structures have been extremely difficult to replicate. Within this context, in this Bachelor’s Degree project the microstructure and the micromechanical properties will be investigated of a ceramic-ceramic composite inspired on natural materials (alumina/alumina nanoparticles reinforced glass), also known as a bioinspired material.
After conducting a thorough bibliographic evaluation, a scarce number of studies have been found on this topic. Here, a study is going to be carried out mainly focused on micromechanical properties as well as detailed analysis as a function of the lamella orientation by means of advanced characterization techniques such as Field Emission Scanning Electron Microscopy or Focused Ion Beam (FESEM/FIB). The assessment and correlation of the microstructure with the mechanical properties is crucial so as to enhance the performance of these materials and to enlarge their lifetime under severe working conditions. This way, a more accurate data is going to be obtained about the behavior of those materials in situations close to their final working conditions.
In this project, a systematic macro-, micro- and nanometric mechanical study has been conducted in three different ceramic/ceramic samples inspired by natural materials, each one with a different platelet orientation. The methodic investigation includes the study of the mechanical properties (indentation tests at different loads) under a wide variety of conditions in order to induce different stress fields and damage scenarios. Special attention has been paid to analyze the main damage and the fracture mechanisms in the surrounding area of the indentation imprint as a function of the platelet orientation by advanced characterization techniques such as FESEM, FIB and Atomic Force Microscope.
The results show that the micromechanical properties (e.g. hardness and elastic modulus) determined at room temperature are not crucially affected by the platelet orientation, obtaining values around 20 GPa and 400 GPa of hardness and elastic modulus, respectively. No cracks are induced at the corners of the imprints performed by using a cube-corner indenter and, subsequently, the indentation fracture toughness is not possible to be determined. Under these circumstances, the plasticity index is established in order to qualitatively estimate this parameter.
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