Negi V, Picu R C
Department of Mechanical, Aerospace and Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180, USA.
Soft Matter. 2019 Jul 24;15(29):5951-5964. doi: 10.1039/c9sm00658c.
We present a study of the mechanical behavior of planar fibrous mats stabilized by inter-fiber adhesion. Fibers of various degrees of tortuosity and of infinite and finite length are considered in separate models. Fibers are randomly distributed, are not cross-linked, and interact through adhesion and friction. The variation of structural parameters such as the mat thickness and the mean segment length between contacts along given fibers with the strength of adhesion is determined. These systems are largely dissipative in that most of the work performed during deformation is dissipated frictionally and only a small fraction is stored as strain energy. The response of the mats to tensile loading has three regimes: a short elastic regime in which no sliding at contacts is observed, a well-defined sliding regime characterized by strain hardening, and a rapid stiffening regime at larger strains. The third regime is due to the formation of stress paths after the fiber tortuosity is pulled out and is absent in mats of finite length fibers. Networks of finite length fibers lose stability during the second regime of deformation. The scaling of the yield stress, which characterizes the transition between the first and the second regimes, and of the second regime's strain hardening modulus, with system parameters such as the strength of adhesion and friction and the degree of fiber tortuosity are determined. The strength of mats of finite length fibers is also determined as a function of network parameters. These results are expected to become useful in the design of electrospun mats and other planar fibrous non-cross-linked networks.
我们展示了一项关于通过纤维间粘附作用稳定的平面纤维垫力学行为的研究。在不同模型中考虑了各种弯曲程度以及无限长和有限长的纤维。纤维随机分布，不发生交联，并通过粘附和摩擦相互作用。确定了诸如垫厚度以及沿给定纤维的接触点之间的平均段长度等结构参数随粘附强度的变化。这些系统在很大程度上是耗散性的，因为在变形过程中所做的大部分功通过摩擦耗散，只有一小部分作为应变能存储起来。纤维垫对拉伸载荷的响应有三个阶段：一个短弹性阶段，在此阶段未观察到接触点处的滑动；一个定义明确的滑动阶段，其特征为应变硬化；以及在较大应变时的快速硬化阶段。第三个阶段是由于纤维弯曲度被拉出后应力路径的形成，并且在有限长纤维的垫中不存在。有限长纤维网络在变形的第二个阶段失去稳定性。确定了表征第一和第二阶段之间转变的屈服应力以及第二阶段的应变硬化模量随诸如粘附强度、摩擦以及纤维弯曲度等系统参数的标度关系。有限长纤维垫的强度也被确定为网络参数的函数。这些结果有望在电纺垫和其他平面纤维非交联网络的设计中发挥作用。
