Abstract
Various modeling approaches simplify and parametrize the complex network structure of nanoporous gold (NPG) for studying the structure–property relationship based on artificially generated structures. This paper presents a computational efficient and versatile finite element method (FEM) beam model that is based on skeletonization and diameter information derived from the original 3D focused ion beam-scanning electron microscope (FIB-SEM) tomography data of NPG. The geometrical skeleton network is thoroughly examined for a better understanding of the NPG structure. A skeleton FEM beam model is derived that can predict the macroscopic mechanical behavior of the material. Comparisons between the mechanical response of this skeleton beam model and a solid FEM model are conducted. Results showed that the biggest-sphere diameter algorithm implemented in the open-source software FIJI, commonly used for geometrical analysis of microstructural data, overestimates the diameter of the curved NPG ligaments. The larger diameters lead to a significant overestimation of macroscopic stiffness and strength by the skeleton FEM beam model. For a parabolic shaped ligament with only 20% variation in its diameter, a factor of more than two was found in stiffness. It is concluded that improved algorithms for image processing are needed that provide accurate diameter information along the ligament axis.
Highlights
Nanoporous gold (NPG) made by dealloying allows producing macroscopic millimeter- or even centimeter-sized porous bodies with a solid fraction around 30% [1,2,3,4]
From first 3D finite element method (FEM) modeling of the ligament network with solid elements and an FEM beam model the effective load-bearing ring structure was found to govern the mechanical behavior, rather than the solid volume fraction proposed by Gibson–Ashby for open-cell foams [19]
To study the influence of different possible discretization approaches, the same cutout of the representative volume element (RVE) is illustrated in Figure 6b–d for each skeleton FEM beam model, and discussed in the following
Summary
Nanoporous gold (NPG) made by dealloying allows producing macroscopic millimeter- or even centimeter-sized porous bodies with a solid fraction around 30% [1,2,3,4]. From first 3D FEM modeling of the ligament network with solid elements (full structure) and an FEM beam model (straight beams connecting the junctions) the effective load-bearing ring structure was found to govern the mechanical behavior, rather than the solid volume fraction proposed by Gibson–Ashby for open-cell foams [19]. This was shown independently by Liu et al [21,22] from macroscopic compression experiments with continuous measurement of Young’s modulus and strength that allowed to derive an effective solid fraction based on the Gibson–Ashby scaling laws. The validated modeling technique will allow producing larger sets of computer-generated data as basis for studying structure-property relationships in the future
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