Negi V, Picu R C
Department of Mechanical, Aerospace and Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180, USA.
Soft Matter. 2021 Nov 24;17(45):10186-10197. doi: 10.1039/d0sm01297a.
Many biological and soft artificial materials contain a random network of non-crosslinked fibers as their main structural component. The excluded volume interactions (contact forces) at fiber contacts control the mechanical behavior of these systems. This physics has been studied extensively in compression, but little is known about the relation between network structure and its mechanical response in tension. In particular, although occasionally used conjecturally, the notion of fiber entanglements in athermal networks is not well defined, nor is it clear what role entanglements play in athermal network mechanics. The primary contribution of this work is the introduction of a measure of the degree of entanglement of a system of random athermal fibers, and the definition of its relationship with the mechanical behavior of the network. Entanglements confine the fibers during tensile loading, reduce the auxetic effect in mat-like networks, and maintain the inter-fiber contact density. In the absence of this contribution, reduction of the contact density during tensile loading due to auxeticity results in stress reduction. Entanglements stabilize the network a tensegrity mechanism similar to that operating in woven materials and lead to network stiffening. The relation between the proposed measure of entanglements and the fiber volume fraction is defined. The effect of inter-fiber friction on the mechanics of entangled mat-like non-crosslinked fiber networks is also evaluated.
许多生物材料和柔软的人工材料都含有由非交联纤维构成的随机网络作为其主要结构成分。纤维接触处的排除体积相互作用（接触力）控制着这些系统的力学行为。这种物理学原理在压缩方面已得到广泛研究，但对于网络结构与其拉伸力学响应之间的关系却知之甚少。特别是，尽管偶尔会有人推测性地使用，但无热网络中纤维缠结的概念并未得到很好的定义，而且缠结在无热网络力学中所起的作用也不清楚。这项工作的主要贡献在于引入了一种衡量随机无热纤维系统缠结程度的方法，并定义了其与网络力学行为的关系。缠结在拉伸加载过程中限制纤维，减少类似垫子的网络中的负泊松比效应，并维持纤维间的接触密度。如果没有这种作用，由于负泊松比导致的拉伸加载过程中接触密度的降低会导致应力减小。缠结使网络稳定——这是一种类似于在编织材料中起作用的张拉整体机制，并导致网络变硬。定义了所提出的缠结度量与纤维体积分数之间的关系。还评估了纤维间摩擦对缠结的类似垫子的非交联纤维网络力学的影响。
