标题： 使用有限元模型的扭绞和缠绕聚合物致动器的驱动机制 显示英文标题

标题： Actuation mechanisms in twisted and coiled polymer actuators using finite element model

摘要： 扭曲和卷曲聚合物执行器（TCPAs）与其他执行器相比具有大行程和大比功的优势。 已经进行了广泛的实验研究以了解其驱动响应，然而，尚未使用包含完整材料描述的计算模型来深入探究导致其大驱动的潜在机制。 在本工作中，我们开发了一个三维有限元模型，该模型包括制造过程的物理原理，以模拟在各种加载和边界条件下的TCPA驱动。 该模型与实验数据进行验证，并用于探索在自由和等压条件下驱动的因素。 该模型捕捉了纤维扭转角度的物理原理以及TCPA驱动响应中同手性和异手性的区别。 模拟结果显示，无论弹性张量是否具有各向异性或各向同性，热膨胀系数（CTE）矩阵的各向异性在大驱动中起着主要作用。 我们进一步研究了热膨胀各向异性的程度，参数研究表明，即使材料在纤维的两个方向上具有正或负的CTE，TCPA驱动的关键在于热膨胀不匹配的绝对值。 此外，我们通过将环氧树脂和空心尼龙管结合，提出了一种新的基于壳-芯复合材料的TCPA概念，以抑制TCPA的蠕变。 结果表明，可以通过调节环氧树脂芯的体积分数来获得所需的驱动，同时提供更刚性和抗蠕变的响应。 这一框架为探测各种类型的TCPAs并提高其驱动性能提供了更广泛的应用。 显示英文摘要

摘要： Twisted and coiled polymer actuators (TCPAs) offer the advantages of large stroke and large specific work as compared to other actuators. There have been extensive experimental investigations towards understanding their actuation response, however, a computational model with full material description is not utilized to probe into the underlying mechanisms responsible for their large actuation. In this work, we develop a three-dimensional finite element model that includes the physics of the fabrication process to simulate the actuation of TCPA under various loading and boundary conditions. The model is validated against the experimental data and used to explore the factors responsible for actuation under free and isobaric conditions. The model captures the physics of the angle of twist in the fiber and the distinction between the homochiral and heterochiral nature of TCPA actuation response. The simulations show that the anisotropy in the thermal expansion coefficient (CTE) matrix plays a major role in large actuation irrespective of the anisotropy or isotropy in the elasticity tensor. We further investigate the extent of anisotropy in thermal expansion and the parametric studies show that the key for TCPA actuation is the absolute value of mismatch in thermal expansion even if the material has positive or negative CTE in both directions of the fiber. Furthermore, we propose a new shell-core composite-based TCPA concept by combining the epoxy and hollow Nylon tubes to suppress the creep in TCPA. The results show that the volume fraction of epoxy-core can be tuned to attain a desired actuation while offering a stiffer and creep-resistant response. This framework provides a wider application for probing various kinds of TCPAs and enhancing their actuation performance.