PSI - Issue 66

Umberto De Maio et al. / Procedia Structural Integrity 66 (2024) 502–510 Author name / Structural Integrity Procedia 00 (2025) 000–000

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3. Computational model and numerical results The investigated microstructure, inspired by the marine glass sponges, represents a geometry evolution from the work of (Fernandes et al., 2021), who had already analyzed the behavior of lattice structures subjected to uniaxial compression along the vertical direction. The geometry was optimized to maximize the critical buckling strain by adopting a gradient-free optimization procedure. In this work the new proposed geometry is characterized by a unit cell composed of a square frame and a diagonal one made by an alternating chain of elliptical and circular features instead of straight features, as reported in Fig.2. This configuration was chosen to provide greater flexibility for geometric optimization by allowing thicknesses to vary independently between elliptical and circular sections.

Fig. 2. Geometry conceptualization of the glass-sponge microstructure unit cell.

Seven primary dimensions are defined in the new design: L, S, S 1 , S 2 ,  e ,  s ,  e , together with three dimensionless parameters K 1 , K 2 , and K 3 with respect to the entire geometry was parametrized. The unit cell’s length and height are denoted by L = 1.5 cm. The parameters S 1 and S 2 define the minor and major axes of the elliptical shapes, respectively, with 1 1 / ( 2 ) S L K S    and 2 ( 2 / 2 ) S L S   . The primary circular elements are denoted by S , representing the basic pore openings uniformly distributed throughout the microstructure. The thickness of the elliptical and circular features are denoted by 2 0.05 , e c e L K      respectively. In contrast, the thickness of the square frames is denoted by 3 s e K    , where 3 1 2 ( , ) K K K is a function of K 1 and K 2 which is determined to obtain a percentage of solid volume fraction equal to 29.8%. Tab.1 reports the geometrical parameters adopted as the starting point of the optimization procedure.

Table 1. Initial geometrical parameters for K 1 = 2, K 2 = 1.086, K 3 = 1.853. Geometrical parameters Value Unit L 1.5 cm S = S 1 0.439 cm S 2 0.62 cm  e 0.075 cm  c  0.069 cm  s  0.139 cm

Regarding the discretization of the geometry, the numerical model was implemented using approximately 10,000 triangular elements, with mesh convergence analysis showing that this resolution was sufficient to describe the behavior of the microstructure under load accurately. The model was implemented in COMSOL Multiphysics under