Surface Instability in a Nematic Elastomer.
Surface Instability in a Nematic Elastomer.
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DOI：
10.1103/physrevlett.131.238101
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发表时间：
2023-03
影响因子：
8.6
通讯作者：
Morgan Barnes;F. Feng;J. Biggins
中科院分区：
文献类型：
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作者：
Morgan Barnes;F. Feng;J. Biggins
液晶弹性体（LCEs）是一种软相变固体，在加热时表现出大的可逆收缩，类似金石的软模式，以及由此产生的微观结构不稳定性。我们将一个平面LCE板加热到各向同性，夹紧下表面，然后冷却回向列。夹紧防止宏观伸长，产生压缩和微观结构。我们看到自由表面失稳，采用振幅和波长与厚度相似的地形。为了理解不稳定性，我们数值计算了“非理想”LCE能量的微观结构弛豫。线性稳定性表现为一种类似biot的无标度不稳定性，但具有斜波矢量。然而，仿真和实验表明，与经典的弹性折痕不同，不稳定性在没有尖点或滞后的交叉线中达到顶峰，并且完全由低应力软模态构成。
Liquid crystal elastomers (LCEs) are soft phase-changing solids that exhibit large reversible contractions upon heating, Goldstone-like soft modes, and resultant microstructural instabilities. We heat a planar LCE slab to isotropic, clamp the lower surface, then cool back to nematic. Clamping prevents macroscopic elongation, producing compression and microstructure. We see that the free surface destabilizes, adopting topography with amplitude and wavelength similar to thickness. To understand the instability, we numerically compute the microstructural relaxation of a "nonideal" LCE energy. Linear stability reveals a Biot-like scale-free instability, but with oblique wave vector. However, simulation and experiment show that, unlike classic elastic creasing, instability culminates in a crosshatch without cusps or hysteresis, and is constructed entirely from low-stress soft modes.