PSI - Issue 40

V. Kibitkin et al. / Procedia Structural Integrity 40 (2022) 223–230

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V. Kibitkin et al/ Structural Integrity Procedia 00 (2022) 000 – 000

correlation method is widely used for this purpose that provides high measurement accuracy, good spatial resolution and relatively simple data processing algorithms (see e.g., Sutton et al. (2009) or Kibitkin et al. (2009)). The behavior of highly porous ceramics under compressive loading is characterized by the presence of inelastic deformation due to forming microcracks (see Chen et al. (2021)). The latter contribute to the accumulation and movement of local volumes of material into the pore space. Porous ceramics are widely used in various applications (see Chen et al. (2021)) where high mechanical properties are required. Each pore can be a stress concentrator suitable for the crack initiation, and therefore the level of porosity is a factor that determines the behavior of the ceramic under load. It is known (see Carlesso et al. (2013)) that segmented ceramic materials can be more tolerant to defects and inhomogeneities that appear arising under loading as compared to monolithic materials. Preliminary experiments on using the DIC method for investigating behaviors of porous segmented alumina under compression loading have shown the practicability of this method for studying the evolution of segmented ceramics under loading (see Kibitkin et al. (2021)). The aim of this work was to identify the main features of the structural evolution and deformation of porous segmented alumina during compression using the DIC. 2. Materials and Methods The samples of segmented ceramics were prepared according to the process described elsewhere (see Kibitkin et al. (2021)). Evaporation of paraffin and ultra-high molecular weight polyethylene, mixed with aluminum oxide powder for slip casting and subsequent sintering at 1350 ºС for 1 hour, made it possible to obtain segmented porous aluminum oxide ceramics. Such ceramics with a total porosity of 50% structurally consisted of grains of polycrystalline alumina with internal pores of ~ 4 μm, large pores ~ 120 μm, and a network of inhomogeneities that subdivide the sample into segments with a size of ~ 210 μm (Fig. 1). Inhomogene ities, similar to extended pore channels (Fig. 1), arise as a result of the opening of a crack in a raw sample under gas pressure as a result of vaporization of paraffin, which begins at temperatures of ~ 150° C (see Kibitkin et al. (2021) ) and subsequent sintering, which is partially healed by such crack.

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Fig. 1. SEM images of sintered porous segmented ceramics. 1- large pores; 2-extended inhomogeneities; 3- small pores.