Abstract Carbon nanotube (CNT) yarns are synthetic nanomaterials of interest for diverse applications. To bring fundamental understanding into the yarn formation process, we perform mesoscopic scale distinct element method (mDEM) simulations for the stretching of CNT networks. The parameters used by mDEM, including the mesoscale friction, are based on full atomistic results. By bridging across the atomistic and mesoscopic length scales, our model predicts accurately the mechanical response of the network over a large deformation range. At small and moderate deformations, the microstructural evolution is dominated by zipping relaxations directed along the applied strain direction. At larger deformations, the occurrence of energetic elasticity promotes yarn densification, by lowering CNT waviness and eliminating squashed pores. Next, by varying the mesoscopic dissipation as well as the network structure, we reveal that the mesoscale friction and film morphology are key factors for the yarn formation: While lack of friction compromises the strain-induced alignment process, phononic and polymeric friction promote CNT alignment by enabling load transfer and directed zipping relaxations, especially in networks containing long and entangled CNTs. Yarns drawn from cellular networks are shown instead to maintain high porosity, even with enhanced polymeric friction.

中文翻译：

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细观摩擦和网络形态控制碳纳米管纱线的力学和加工

摘要 碳纳米管 (CNT) 纱线是具有多种应用的合成纳米材料。为了对纱线形成过程有基本的了解，我们对 CNT 网络的拉伸进行了细观尺度不同元素方法 (mDEM) 模拟。mDEM 使用的参数（包括中尺度摩擦）基于完整的原子结果。通过跨越原子和介观长度尺度，我们的模型可以准确预测网络在大变形范围内的机械响应。在小和中等变形下，微观结构演变由沿施加应变方向的压缩松弛主导。在较大的变形下，能量弹性的出现通过降低 CNT 波纹度和消除压扁的孔隙来促进纱线致密化。下一个，通过改变细观耗散和网络结构，我们发现细观摩擦和薄膜形态是纱线形成的关键因素：虽然缺乏摩擦会损害应变诱导的排列过程，但声子和聚合物摩擦通过使负载转移和定向压缩松弛，尤其是在包含长且缠结的 CNT 的网络中。取而代之的是，从蜂窝网络中提取的纱线即使在聚合物摩擦力增强的情况下也能保持高孔隙率。声子和聚合物摩擦通过实现负载转移和定向压缩松弛来促进 CNT 对齐，尤其是在包含长且缠结的 CNT 的网络中。取而代之的是，从蜂窝网络中提取的纱线即使在聚合物摩擦力增强的情况下也能保持高孔隙率。声子和聚合物摩擦通过实现负载转移和定向压缩松弛来促进 CNT 对齐，尤其是在包含长且缠结的 CNT 的网络中。取而代之的是，从蜂窝网络中提取的纱线即使在聚合物摩擦力增强的情况下也能保持高孔隙率。