Effect of microstructure heterogeneity on the damage resistance of nacre-like alumina: Insights from image-based discrete simulations

Abstract

Recently, several types of nacre-like materials have been developed using various methods. However, the resulting materials exhibit a significant randomness and defects compared to natural nacre. Therefore, evaluating the influence of these microstructural variations on the material's mechanical behavior is of high interest for the development of nacre-like materials and their industrial scale-up. In this work, we present an original method that allows the modeling of complex morphology of brick and mortar materials, by combining Discrete Element Method and Electron Backscatter Diffraction images. Using different realistic microstructures we studied the effect of the microstructural variations on crack propagation and damage resistance. The obtained results were compared to the regular microstructure of nacre and showed a non-negligible decrease of mechanical properties.

Toughening mechanisms in nacre-like alumina revealed by in-situ imaging of stress

“…3 and 4). This is consistent with the results of numerical simulations that used the observed microstructures to show cracks propagate at higher stress around bundles of misoriented platelets, thus contributing to toughening the composite (Radi et al, 2021). These defects likely contribute to the increasing toughness (R curve) of the nacre-like alumina.…”

“…However, the actual structure of nacre-like ceramics is more complex, with heterogeneity in alumina platelet size and imperfect orientations during the fabrication (Saad et al, 2020). Simulations based on actual microstructures have shown the importance of local imperfections of the microstructure on the toughness of the composite (Marcinkowska, 2018;Radi et al, 2021). Imaging of local stress around the propagating crack highlights the interaction of the crack with the imperfections of the microstructure.…”

“…Establishing quantitative links between nano-to microscopic structures and bulk mechanical properties determined in standardized fracture tests requires additional mechanical modeling at various scales and methods that enable imaging the effects of microstructures on the mechanical behavior. For instance, structural defects (such as local misalignments, variable platelet size) of real microstructures spanning few tens of micrometers can be modeled by DEM, which suggests that they may have a significant effect on crack propagation (Radi et al, 2021). To validate these results, we developed in situ spectroscopic and scanning electron microscopy (SEM) imaging of stress field and microstructure during a bending test on nacre-like alumina.…”

Complex Composites Built through Freezing

“…Which toughening mechanisms contribute to Understanding the mechanical properties of these complex composites. Complementary analysis at different scales is required, from macroscopic tests (single-edge notched beam (SENB) 33 and R-curve measurements) to smaller-scale tests (nanoindentation 35 and microcantilever 34 ), modeling (discrete element modeling 38 ), and Raman spectroscopy. 40 The SENB image is from DOI: 10.6084/m9.figshare.…”

“…36 The models have since been made more realistic by generating real microstructures using actual micrographs of nacre-like alumina. 38 It should also be noted that this is a complex multiparameter optimization problem. Because several parameters and features can be adjusted, only the local optimum can be achieved.…”