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Oral Poster Presentation

On the way to mass production of unit-cell based auxetic materials

Wednesday (07.10.2020)
19:04 - 19:07

Auxetic materials exhibit unique properties which are not found in nature - like a negative Poisson´s Ratio - originating from a defined internal structure of the material, based on small repeating building blocks, the unit-cells. Origami is the art of paper folding in the Japanese culture and established as an engineering design method. One of the most frequently regarded structures based on origami folding is the Miura-Ori pattern. The unit cell of this pattern consists of four identical parallelogram shaped surfaces which form a foldable 2D structure. A layer formed of a 2D concatenation of such unit-cells has an auxetic behaviour and can be compressed to a compact or unfolded to flat structure. Such 2D structures can be stacked to 3D structures also exhibiting auxetic behaviour. The response of single or stacked unit-cell based materials to dynamic compression and the influence of various geometric parameters have been studied in literature on 3D printed samples or pressed metal sheets.

In view of a future production technique suitable for auxetic bulk materials in big volumes, this work investigates the quasi-static behaviour of single and stacked structured layers in tensile test, which has rarely been examined numerically and experimentally with other production techniques than 3D printing. The single layers were manufactured using a thermoplastic polyurethane in a thermoforming process. In a first step, the quasi-static behaviour of single layers was analysed in tensile tests. In order to achieve a bulk material, layers with various folded angles were stacked and also analysed. Furthermore, the type of connection between the different layers and the influence of different connection methods were investigated. The paper compares the results from numerical simulations of the bulk materials properties and experimental results.

 

Speaker:
Angela Schwarz
Fraunhofer Institute for Chemical Technology ICT
Additional Authors:
  • Franziska Wenz
    Fraunhofer Institute for Mechanics of Materials IWM
  • Konstantin Kappe
    Fraunhofer Institute for High-Speed Dynamics, Ernst-Mach-Institut, EMI
  • Tobias Lichti
    Fraunhofer Institute for Industrial Mathematics ITWM
  • Dr. Christof Hübner
    Fraunhofer Institute for Chemical Technology ICT