Stimulus activated structures that deform from a reference to target configurations are used in various fields such as soft robotics, smart materials, and actuators. Examples of stimuli include electric and magnetic fields, swelling, and temperature. The design of stimulus activated structures requires a comprehensive understanding of the relations between geometry, material properties, structure composition, and the influence of the chosen stimulus. With the aim of better understanding these relations, this work employs moderate rotations theory to model the thermo-mechanical response of multi-layered polymeric struts in a wide range of temperatures. In particular, the transition from a glassy to a rubbery state is explicitly discussed. Implicit equations that relate the material properties and the geometry to the thermally-induced deformation are developed. To illustrate the merit of the model, we investigate the thermo-mechanical behavior of homogeneous and heterogeneous multi-layered struts under two boundary conditions - free-standing and pinned. We show that multi-layered beams with a mismatch in the thermal and elastic properties bend as a result of temperature change. Interestingly, the glass-transition temperature can result in the reversal of bending direction. We follow with simulations of thermally-activated polymer-based bi-layer struts with typical properties to demonstrate the applicability of the proposed design. This framework can be used as a guideline and an inverse design tool for the selection of materials and geometries for thermally-activated shape-morphing lattice-based structures that are capable of achieving multiple shape-shifts with a single stimulus. Additionally, this work can be readily extended to other stimuli and thus serves as a foundation for the effective design of stimulus activated structures capable of polymorphism.

从参考到目标配置变形的刺激激活结构用于各种领域，例如软机器人、智能材料和执行器。刺激的例子包括电场和磁场、膨胀和温度。刺激激活结构的设计需要全面了解几何、材料特性、结构组成和所选刺激的影响之间的关系。为了更好地理解这些关系，这项工作采用适度旋转理论来模拟多层聚合物支柱在很宽的温度范围内的热机械响应。特别是，明确讨论了从玻璃态到橡胶态的转变。开发了将材料特性和几何形状与热致变形相关联的隐式方程。为了说明该模型的优点，我们研究了均质和异质多层支柱在两种边界条件（独立式和固定式）下的热机械行为。我们表明，热和弹性特性不匹配的多层梁会因温度变化而弯曲。有趣的是，玻璃化转变温度会导致弯曲方向的逆转。我们随后对具有典型特性的热活化聚合物基双层支柱进行了模拟，以证明所提议设计的适用性。该框架可用作指导和逆向设计工具，用于为热激活形状变形晶格结构选择材料和几何形状，这些结构能够通过单个刺激实现多种形状变化。此外，这项工作可以很容易地扩展到其他刺激，因此可以作为有效设计具有多态性的刺激激活结构的基础。