Department of Mechanical, Aerospace and Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180, United States.
Department of Mechanical, Aerospace and Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180, United States.
J Mech Behav Biomed Mater. 2019 Jun;94:1-9. doi: 10.1016/j.jmbbm.2019.02.023. Epub 2019 Feb 21.
Most biological fibrous materials are hierarchical, in the sense that fibers of finite length assemble in bundles, which then form networks with structural role. Examples include collagen, silk, fibrin and microtubules. Some artificial fiber-based materials share this characteristic, examples including carbon nanotube (CNT) yarns and unidirectional composites. Here we study bundles in which filaments do not break, while bundle rupture happens by the failure of inter-filament crosslinks, followed by pull-out. In all cases, the crosslinks are randomly distributed along interfaces. The strength of such bundles depends on material parameters of the filaments and crosslinks, such as their stiffness and strength, and on the cross-link density. We focus on the dependence of the bundle strength on two parameters: filament waviness and filament staggering. Bundles with regular staggering are stronger than those with stochastic staggering. We identify the optimal regular staggering that maximizes the strength. Filament waviness increases the strength of stochastically staggered bundles at constant crosslink density but decreases the strength of regularly staggered bundles. Results for bundles with permanent crosslinks, which never reform once they break, as well as transient crosslinks capable of reforming during deformation are presented, and it is shown that the general trends are independent of the nature of the crosslinks. The results are discussed in the context of collagen and carbon nanotube bundles.
大多数生物纤维材料都是分层的，从这个意义上说，有限长度的纤维在束中组装，然后这些束形成具有结构作用的网络。例如胶原、丝、纤维蛋白和微管。一些基于人工纤维的材料具有这种特性，例如碳纳米管（CNT）纱线和单向复合材料。在这里，我们研究了其中纤维不会断裂的束，而束的断裂是通过纤维间交联的失效以及随后的拔出而发生的。在所有情况下，交联都是沿着界面随机分布的。这种束的强度取决于纤维和交联的材料参数，例如它们的刚度和强度以及交联密度。我们专注于束强度对两个参数的依赖关系：纤维的波浪度和纤维交错度。具有规则交错的束比具有随机交错的束强。我们确定了最佳的规则交错，以最大化强度。在恒定交联密度下，波浪度增加了随机交错束的强度，但降低了规则交错束的强度。还给出了具有永久性交联的束（一旦断裂就永远不会重新形成）和在变形过程中能够重新形成的瞬时交联的结果，并且表明一般趋势与交联的性质无关。结果在胶原和碳纳米管束的背景下进行了讨论。
