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Designing Shape Morphing Behavior through Local Programming of Mechanical Metamaterials

: Wenz, Franziska; Schmidt, Ingo; Leichner, Alexander; Lichti, Tobias; Baumann, Sascha; Andrae, Heiko; Eberl, Christoph

Volltext ()

Advanced Materials 33 (2021), Nr.37, Art. 2008617, 8 S.
ISSN: 0935-9648
ISSN: 1521-4095
Deutsche Forschungsgemeinschaft DFG
Germany's Excellence Strategy; EXC-2193/1-390951807
Zeitschriftenaufsatz, Elektronische Publikation
Fraunhofer ICT ()
Fraunhofer ITWM ()
Fraunhofer IWM ()
homogenization; material design; mechanical metamaterials; Multiscale Simulation; programmable material; shape morphing

Shape morphing implicates that a specific condition leads to a morphing reaction. The material thus transforms from one shape to another in a predefined manner. In this paper, not only the target shape but rather the evolution of the material's shape as a function of the applied strain is programmed. To rationalize the design process, concepts from informatics (processing functions, for example, Poisson's ratio (PR) as function of strain: ν = f(ε) and if-then-else conditions) will be introduced. Three types of shape morphing behavior will be presented: (1) achieving a target shape by linearly increasing the amplitude of the shape, (2) filling up a target shape in linear steps, and (3) shifting a bulge through the material to a target position. In the first case, the shape is controlled by a geometric gradient within the material. The filling kind of behavior was implemented by logical operations. Moreover, programming moving hillocks (3) requires to implement a sinusoidal function εy = sin (εx) and an if-then-else statement into the unit cells combined with a global stiffness gradient. The three cases will be used to show how the combination of mechanical mechanisms as well as the related parameter distribution enable a programmable shape morphing behavior in an inverse design process.