Normal stress anisotropy and marginal stability in athermal elastic networks
Normal stress anisotropy and marginal stability in athermal elastic networks
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非热弹性网络中的法向应力各向异性和边际稳定性
DOI：
10.1039/c8sm02192a
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发表时间：
2019
期刊：
影响因子：
3.4
通讯作者：
MacKintosh, F. C.
中科院分区：
文献类型：
--
作者：
Shivers, Jordan L.;Feng, Jingchen;Sharma, Abhinav;MacKintosh, F. C.
半柔性生物聚合物（例如胶原蛋白）的水凝胶已被证明在剪切应变下会轴向收缩，这与大多数弹性材料观察到的轴向膨胀相反。最近的工作表明，这种行为可以从水凝胶的多孔、双组分性质和随之而来的时间依赖性压缩性来理解。扭转流变仪测量的表观法向应力仅反映长（可压缩）时间尺度上轴向分量 σzz 的拉伸贡献，在短（不可压缩）时间尺度上交叉到第一法向应力差 N1 = σxx – σzz。虽然 N1 的行为对于经历仿射剪切变形的各向同性粘弹性材料来说是很好理解的，但生物聚合物网络通常是各向异性的并且非仿射变形。在这里，我们对亚等静压、无热半柔性聚合物网络中剪切作用下产生的法向应力进行了数值研究。我们表明，此类系统表现出与仿射行为的强烈偏差，并且这些异常是由作为应变函数的刚度转变控制的。
Hydrogels of semiflexible biopolymers such as collagen have been shown to contract axially under shear strain, in contrast to the axial dilation observed for most elastic materials. Recent work has shown that this behavior can be understood in terms of the porous, two-component nature and consequent time-dependent compressibility of hydrogels. The apparent normal stress measured by a torsional rheometer reflects only the tensile contribution of the axial component σzz on long (compressible) timescales, crossing over to the first normal stress difference, N1 = σxx − σzz at short (incompressible) times. While the behavior of N1 is well understood for isotropic viscoelastic materials undergoing affine shear deformation, biopolymer networks are often anisotropic and deform nonaffinely. Here, we numerically study the normal stresses that arise under shear in subisostatic, athermal semiflexible polymer networks. We show that such systems exhibit strong deviations from affine behavior and that these anomalies are controlled by a rigidity transition as a function of strain.