PSI - Issue 32

A.S. Shalimov et al. / Procedia Structural Integrity 32 (2021) 230–237 Shalimov A.S., Tashkinov M.A. / Structural Integrity Procedia 00 (2019) 000–000

231

2

ligaments has a significant impact on the mechanical properties of such a material. As the diameter of the ligaments decreases, the hardness and strength of the structure increases. This is due to the large surface area to volume ratio and the high individual local strength of the ligaments (Griffiths et al., 2020). Nanoporous metals possess features that are similar to foams, their heterogeneous structure can be modelled as an open-cell bicontinuous media.

Fig. 1. Scanning electron microscopy image of a sample of nanoporous gold (Jiao and Huber, 2017)

The long list of possible applications of nanoporous metals includes energy storage and conversion in fuel cells, hydrogen storage, purification and separation of gases and liquids, biomedical devices and others (Polarz and Smarsly, 2002). Recent studies have also investigated application of such metals as a functional material for catalysis, actuators and sensing (Ding and Chen, 2009; Stenner et al., 2016). Research in this area is driven by the desire to create materials with special physical, chemical and mechanical properties. The porous phase can be filled with a material that differs from the solid phase material, thereby producing unique nanocomposites (Bargmann et al., 2016; Griffiths et al., 2020). The mechanical response of a nanoporous structure depends on the material model of the solid phase, the overall dimensions, applied load as well as morphological features such as pore size, pore geometry, pore distribution and ligament size. The influence of structural morphology on the deformation of nanoporous metals cannot be fully assessed by experimental methods. Therefore, it is useful to investigate the microstructural properties of such a material using a representative volume element (RVE) concept at nanoscale. By taking into account random distribution of the ligament network and the resulting behavior, the relationship between the effective properties at different length-scale can be derived. An efficient approach to the study of nanoscale cellular structures is advanced numerical simulation. It allows to model the properties and behavior of various random material configurations that would be difficult to examine experimentally. RVE geometry can be successfully modeled using the level-set method, which is based on random Gaussian functions (Bargmann et al., 2016; Shalimov and Tashkinov, 2020; Tashkinov, 2021). The continuum mechanics models of the nanoscale structures can be created based on the simulation results obtained with the molecular dynamics methods at a lower scale (Cox and Dunand, 2011; Li et al., 2019). This paper presents results of numerical modelling of mechanical behavior of bicontinuous porous media with a gold matrix using finite element method as well as results of the analysis of the influence of microstructural parameters on deformation processes for RVEs under tensile and compressive uniaxial load. 2. Models and methods Random geometry of RVEs corresponding to the structure of nanoporous gold was created using the level-set method and a random Gaussian field function. First, a random field based on a Gaussian random function is generated. Secondly, under a special condition, the points of this random field are assigned to either the first phase or the second phase of RVE. In the case of a porous material, one phase is considered as the metal matrix and the second phase as porous. The random Gaussian function is represented as a Fourier series containing random