Mechanical instabilities in soft solids

软固体材料，如凝胶、橡胶、皮肤和肌肉，其特点是能够承受大的弹性应变。这些大变形将几何非线性引入到它们的行为中，这为一系列新的弹性不稳定性奠定了基础，在高载荷下，材料会自发地采用更复杂的形状。这些不稳定性包括众所周知的经典不稳定性，如气球和屈曲，也包括最近发现的不稳定性，如表面折痕和弹性指进。形状形成弹性不稳定性通常被认为是破坏模式，但我们现在了解到，它们已经被进化利用来塑造发育中的器官，并有巨大的潜力被工程师利用来支撑变形装置和小规模的形状制造。这个项目的目的是使用理论和计算工具来加强我们对大应变弹性不稳定性的理解。该项目将从学习阶段开始，专注于推导出一个类似孤子的气球理论，并绘制充气腔中蠕动-气球转变的图谱。然后，该项目的主体将专注于由液晶弹性体(LCE)中发现的大热/光应变引发的弹性不稳定性。特别是，该项目将研究当坚硬的LCE层附着在柔软的基板上，然后导致相对于基板膨胀时发生的折叠/起皱不稳定性。LCE的一个独特特征是，可以通过在制造时压印所需的向列型导向器图案来对膨胀应变进行空间图案化，从而提供对将出现的褶皱图案的控制。这个项目将研究褶皱图案和编码导向器图案之间的关系，最终创造出通过加热或照明而产生设计者地形的表面。该项目正好适用于EPSRC的三个领域：生物物理和软物质物理、连续介质力学和聚合物材料。

Soft solid materials, such as gels, rubbers, skin and muscle, are characterized by their ability to undergo large elastic strains. These large deformations introduce geometric non-linearities into their behaviour, which underpin a wide range of novel elastic instabilities in which, at high load, the material spontaneously adopts a more complicated shape. These instabilities include well known classics such as ballooning and buckling, and also recently uncovered instabilities such as surface creasing and elastic fingering. Shape forming elastic instabilities have normally been thought of as failure modes, but we now understand they have been exploited by evolution to sculpt developing organs, and have great potential for exploitation by engineers to underpin shape-shifting devices and small scale shape fabrication. The aim of this project is to use theoretical and computational tools to enhance our understanding of large strain elastic instabilities. The project will start with a learning phase, focused on deriving a soliton-like theory of ballooning and mapping the peristalsis-ballooning transition in inflated cavities. The main body of the project will then focus on elastic instabilities that are triggered by the large thermal/optical strains found in liquid crystal elastomers (LCEs). In particular, the project will study the folding/wrinkling instabilities that occur when a stiff LCE layer is adhered to a soft substrate then caused to expand relative to the substrate. A unique feature of LCEs is that the expansion strain can be spatially patterned by imprinting a desired nematic director pattern at fabrication, offering control over the wrinkle patterns that will emerge. This project will study the relationship between wrinkle pattern and encoded director pattern, culminating in the creation of surfaces on which designer topography arises via buckling on heating or illumination. This project fits squarely in three EPSRC areas: Biophysics and soft matter physics, continuum mechanics, and polymer materials.