Twisting plays an important role in fabricating twisted actuators and energy harvesters, which require excellent microstructural deformation and interaction properties between different layers. However, the cross-layer microstructural evolution and interaction mechanism of helical structures under twisting and stretching are still unclear. Herein, a multi-layer model is established to theoretically investigate the response of the filaments under twisting and stretching. The results quantitatively indicate that the filaments with a higher twist have more structural evolution and less elongation deformation in the tensile process, which contributes to the increase of ductility. The evolution of the helical angle is also verified by experiments and finite element simulations. Besides, a theoretical method is provided for investigating the mechanical behavior of anisotropic twisted fibers, and the contact pressure is also promoted to understand the twisting-induced densification. The interlayer extrusion reveals that appropriate stretching of twisted fiber is an effective way to densify the loose fibers, and it also provides the theoretical reason for twisting and stretching simultaneously when wringing out a wet towel. We believe that this work would shed light on the interaction mechanism of twisted filaments and provide mechanistic insights into the twisting design of multi-layer helical structures.

中文翻译：

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揭示扭曲结构的微观结构演化和相互作用机制


扭转在制造扭转执行器和能量收集器中发挥着重要作用，这需要优异的微观结构变形和不同层之间的相互作用特性。然而，扭曲和拉伸下螺旋结构的跨层微观结构演化和相互作用机制仍不清楚。在此，建立了多层模型，从理论上研究长丝在扭曲和拉伸下的响应。结果定量表明，捻度较高的长丝在拉伸过程中具有更多的结构演化和更少的伸长变形，这有助于延展性的增加。螺旋角的演变也通过实验和有限元模拟得到验证。此外，还为研究各向异性加捻纤维的力学行为提供了理论方法，并且还促进了接触压力以了解加捻引起的致密化。层间挤压揭示了加捻纤维的适当拉伸是使松散纤维致密化的有效途径，也为拧干湿毛巾时同时加捻和拉伸提供了理论依据。我们相信这项工作将揭示扭曲细丝的相互作用机制，并为多层螺旋结构的扭曲设计提供机制见解。