David Schwarz (University of Freiburg) Mechanical metamaterials switch auxeticity during compression

Termín: 9. 5. 2023
Odkaz: Odkaz na web
Auxetic metamaterials exhibit a fascinating trait under mechanical load. While conventional materials expand, auxetics shrink laterally during compression. Such behavior associated with negative Poisson’s ratio is achieved thanks to the rational geometrical and topological organization of the metamaterial and can therefore be tuned depending on a specific application. Traditional auxetic metamaterials continuously shrink in all directions with an increase in compressive load. Here we propose to analyze the sinusoidal lattice capable of both shrinking and expanding amid mechanical loading, depending on the applied force value. The geometrical change from straight connections (e.g., as in reentrant lattices) to curvy beams (sinusoidal lattice) results in a strain and load-dependent sign of the Poisson’s ratio. Meaning, under compression, negative transverse strain occurs only before the point of self-contact in the metamaterial. Thereafter the observed Poisson’s ratio is positive, thus creating a toggle point for the metamaterial auxeticity. The unit cell geometry determines the critical compressive strain for such a switch. Here we use finite element simulations to characterize this not yet studied phenomenon. We perform mechanical testing on additively manufactured specimens to back numerical predictions. Ultimately, this observed phenomenon can be harnessed in the design of mechanical switches or as an if-then condition for minimum exerted compressive force. With the developed framework, similar metamaterials can be designed with their mechanical behavior tailored to novel use cases.

09.05.2023, 15.00 - 15.30, Room B-366 @ Thákurova 7, 166 29 Prague 6

Za stránku zodpovídá: Ing. Mgr. Radovan Suk