Elucidating the G" overshoot in soft materials with a yield transition via a time-resolved experimental strain decomposition
Elucidating the G" overshoot in soft materials with a yield transition via a time-resolved experimental strain decomposition
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DOI：
10.1073/pnas.2003869117
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发表时间：
2020-09-08
影响因子：
11.1
通讯作者：
Rogers, Simon A.
中科院分区：
文献类型：
--
作者：
Donley, Gavin J.;Singh, Piyush K.;Rogers, Simon A.
表现出屈服行为的材料有许多应用，从涂抹食品和化妆品到直写三维印刷油墨和填充橡胶。它们的关键设计特征是能够在足够的负载或变形下从固体行为转变为流体。尽管其应用广泛，但人们对实际过程中屈服的动态知之甚少，因为转变的非平衡性质阻碍了理解。我们演示了一种迭代间断流变协议，该协议将应变控制振荡剪切与应力控制恢复测试相结合。该技术提供了可恢复和不可恢复应变的实验分解，允许以时间分辨的方式分离对屈服应力材料行为的类固体和类流体贡献。使用该协议，我们研究了屈服材料中损耗模量的超调。我们表明，这种现象是由线性状态下的主要类固体粘弹性耗散转变为较大振幅下的主要类流体塑性流动引起的。我们将其与没有屈服行为的粘弹性液体进行比较和对比，其中粘性流对能量耗散的贡献在整个测试的振幅范围内占主导地位。
Materials that exhibit yielding behavior are used in many applications, from spreadable foods and cosmetics to direct write three-dimensional printing inks and filled rubbers. Their key design feature is the ability to transition behaviorally from solid to fluid under sufficient load or deformation. Despite its widespread applications, little is known about the dynamics of yielding in real processes, as the nonequilibrium nature of the transition impedes understanding. We demonstrate an iteratively punctuated rheological protocol that combines strain-controlled oscillatory shear with stress-controlled recovery tests. This technique provides an experimental decomposition of recoverable and unrecoverable strains, allowing for solidlike and fluid-like contributions to a yield stress material's behavior to be separated in a time-resolved manner. Using this protocol, we investigate the overshoot in loss modulus seen in materials that yield. We show that this phenomenon is caused by the transition from primarily solid-like, viscoelastic dissipation in the linear regime to primarily fluid-like, plastic flow at larger amplitudes. We compare and contrast this with a viscoelastic liquid with no yielding behavior, where the contribution to energy dissipation from viscous flow dominates over the entire range of amplitudes tested.