Wenz Franziska, Schmidt Ingo, Leichner Alexander, Lichti Tobias, Baumann Sascha, Andrae Heiko, Eberl Christoph
Fraunhofer Institute for Mechanics of Materials (IWM), 79108, Freiburg, Germany.
Institute for Microsystems Engineering, Albert-Ludwigs University of Freiburg, 79110, Freiburg, Germany.
Adv Mater. 2021 Sep;33(37):e2008617. doi: 10.1002/adma.202008617. Epub 2021 Aug 2.
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 ε = sin (ε ) 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.
形状变形意味着特定条件会引发变形反应。材料会以预定义的方式从一种形状转变为另一种形状。在本文中，不仅对目标形状进行了编程，还对材料形状随所施加应变的演变进行了编程。为了使设计过程合理化，将引入信息学中的概念（处理函数，例如作为应变函数的泊松比（PR）：ν = f(ε) 以及条件语句）。将展示三种类型的形状变形行为：（1）通过线性增加形状的幅度来实现目标形状，（2）以线性步骤填充目标形状，以及（3）将凸起穿过材料移动到目标位置。在第一种情况下，形状由材料内部的几何梯度控制。填充行为通过逻辑运算来实现。此外，对移动小丘（3）进行编程需要在晶胞中实现正弦函数 ε = sin(ε) 和条件语句，并结合全局刚度梯度。这三种情况将用于展示机械机制的组合以及相关参数分布如何在逆向设计过程中实现可编程的形状变形行为。
