Nonlinear material behaviour of spider silk yields robust webs
Nonlinear material behaviour of spider silk yields robust webs
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DOI：
10.1038/nature10739
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发表时间：
2012-02-02
期刊：
影响因子：
64.8
通讯作者：
Buehler, Markus J.
中科院分区：
文献类型：
--
作者：
Cranford, Steven W.;Tarakanova, Anna;Buehler, Markus J.
天然材料以其精致的设计而闻名，优化了功能，如血管的弹性，骨骼的韧性和珍珠层提供的保护（1-5）。特别有趣的是蜘蛛丝，研究探索了从蛋白质序列（6）到网络几何形状（7）的特性。该材料系统（8）高度适合于满足蜘蛛的许多需求，具有上级机械性能（9-15）。尽管对支撑丝纤维卓越性能的分子设计（1，6，10，13，16，17）以及网状结构的机械特征（18-21）进行了大量研究，但蜘蛛丝的机械特征如何贡献仍然未知蜘蛛网的完整性和性能。在这里，我们报告的网络变形实验和模拟，确定的非线性响应的丝线应力，涉及软化在屈服点和大应变，直到失败的实质性硬化是至关重要的本地化负载引起的变形，并导致机械坚固的蜘蛛网。控制模拟证实，与线性弹性或弹塑性（软化）材料行为相比，非线性应力响应对腹板中的结构缺陷具有更好的上级抵抗力。我们还表明，在分布载荷下，如风所施加的，在屈服点之前，小变形下的丝绸的刚性行为，是必不可少的，在保持网络的结构完整性。因此，丝在纤维网中的上级性能不仅仅是由于其特殊的极限强度和应变，而是由于丝线对应变的非线性响应及其在纤维网中的几何排列。
Natural materials are renowned for exquisite designs that optimize function, as illustrated by the elasticity of blood vessels, the toughness of bone and the protection offered by nacre(1-5). Particularly intriguing are spider silks, with studies having explored properties ranging from their protein sequence(6) to the geometry of a web(7). This material system(8), highly adapted to meet a spider's many needs, has superior mechanical properties(9-15). In spite of much research into the molecular design underpinning the outstanding performance of silk fibres(1,6,10,13,16,17), and into the mechanical characteristics of web-like structures(18-21), it remains unknown how the mechanical characteristics of spider silk contribute to the integrity and performance of a spider web. Here we report web deformation experiments and simulations that identify the nonlinear response of silk threads to stress-involving softening at a yield point and substantial stiffening at large strain until failure-as being crucial to localize load-induced deformation and resulting in mechanically robust spider webs. Control simulations confirmed that a nonlinear stress response results in superior resistance to structural defects in the web compared to linear elastic or elastic-plastic (softening) material behaviour. We also show that under distributed loads, such as those exerted by wind, the stiff behaviour of silk under small deformation, before the yield point, is essential in maintaining the web's structural integrity. The superior performance of silk in webs is therefore not due merely to its exceptional ultimate strength and strain, but arises from the nonlinear response of silk threads to strain and their geometrical arrangement in a web.