Compressive properties of parametrically optimised mechanical metamaterials based on 3D projections of 4D geometries

Gabrielis Cerniauskas, Parvez Alam

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

The design process of 3D mechanical metamaterials is still an emerging field and in this paper, we propose for the first time, a new design and optimisation approach based on 3D projections of 4D geometries (4-polytopes) and evolutionary algorithms. We find that through iterative parametric optimisation, 4-polytope projected mechanical metamaterials can be optimised to achieve both high specific stiffness and high specific yield strengths. Samples manufactured using a low-stereolithography method were tested in compression. We find that optimised tesseracts (8-cell structures) had a higher specific yield strength (22.8 kN m/kg) than that of honeycomb structures tested out-of-plane (19.4 kN m/kg) and a specific stiffness of (0.68 MN m/kg) which is more than 3-fold that of gyroid structures. The compressive strength to solid-modulus ratio of the 8-cell tesseract is very high (3×10−3), exceeding that of out-of-plane honeycombs, which are themselves closer in value to 5-cell pentatopes (2×10−3). 8-cell and 5-cell structures are in the region of one order of magnitude higher than 16-cell and 24-cell structures (∼ 2 × 10−4 − 8 × 10−4) and are hence comparable to nanostructured metamaterials. The 8-cell tesseracts are 18% stiffer, 43% stronger, and 19% tougher in compression than out-of-plane honeycomb structures, but unlike honeycombs, 8-cell tesseracts are 3D structures with cubic symmetry. Architecture has a profound effect on the relative consistency of properties with cubically symmetric structures displaying the greatest levels of consistency in terms of both strength and stiffness reduction as a function of pore space. The results presented in this paper showcase the potential of this new class of mechanical metamaterial based on 3D projected 4-polytopes.
Original languageEnglish
Article number102019
Number of pages14
JournalExtreme Mechanics Letters
Volume61
Early online date29 Apr 2023
DOIs
Publication statusPublished - Jun 2023

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