Thermally-driven semi-crystalline polymer networks are capable to achieve both the one-way shape-memory effect and two-way shape-memory effect under stress and stress-free conditions, therefore representing an appealing class of polymers for applications requiring autonomous reversible actuation and shape changes. In these materials, the shape-memory effects are achieved by leveraging the synergistic interaction between one or more crystalline phases and the surrounding amorphous ones that are present within the network itself. The present paper introduces a general framework for the finite strain continuum phenomenological modeling of the thermo-mechanical and shape-memory behavior of multi-phase semi-crystalline polymer networks. Model formulation, including the definition of phase and control variables, kinematic assumptions, and constitutive specifications, is introduced and thoroughly discussed. Theoretical derivations are general and easily adaptable to all cross-linked systems which include two or more crystalline domains or a single crystalline phase with a wide melting range and manifest macroscopically the one-way shape-memory effect and the two-way shape-memory effect under stress and stress-free conditions. Model capabilities are validated against experimental data for copolymer networks with two different crystalline phases characterized by well-separated melting and crystallization transitions. Results demonstrate the accuracy of the proposed model in predicting all the phenomena involved and in furnishing a useful support for future material and application design purposes.

中文翻译：

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描述多相半结晶网络中形状记忆效应的有限应变连续体现象模型


热驱动半结晶聚合物网络能够在应力和无应力条件下实现单向形状记忆效应和双向形状记忆效应，因此对于需要自主可逆驱动和形状变化的应用来说，它是一类极具吸引力的聚合物。在这些材料中，形状记忆效应是通过利用一个或多个晶相与网络本身中存在的周围非晶相之间的协同相互作用来实现的。本文介绍了多相半结晶聚合物网络的热机械和形状记忆行为的有限应变连续体现象学建模的一般框架。介绍并全面讨论了模型公式，包括相位和控制变量的定义、运动学假设和本构规范。理论推导是通用的，很容易适应所有交联体系，包括两个或多个晶畴或具有较宽熔程的单个晶相，并在宏观上表现出应力和无应力条件下的单向形状记忆效应和双向形状记忆效应。模型功能根据具有两种不同结晶相的共聚物网络的实验数据进行了验证，其特征是分离良好的熔化和结晶转变。结果表明，所提出的模型在预测所有涉及的现象以及为未来的材料和应用程序设计目的提供有用的支持方面是准确的。