Collaborative Research: Dynamics and Propagation of Surface Instabilities in Soft Materials

当软材料被压缩时，它们的表面通常自发地形成具有周期性图案的褶皱、折痕、脊或褶皱。这些模式被称为“表面不稳定性”。在过去的几年里，人们对理解表面不稳定性如何形成产生了极大的兴趣，因为它们在生物系统中无处不在，并且在从微制造到软机器人的工程应用中得到了广泛的应用。然而，几乎所有过去的研究都集中在理解表面不稳定性如何在非常缓慢的压缩下形成，或者忽略了导致这种事件的动力学。该奖项将研究表面不稳定性如何形成并在材料表面传播，作为快速压缩或冲击的结果。导致不稳定的事件的速度是至关重要的，因为它产生了基本上独特的现象，这些现象在大多数物理系统中普遍存在，但仍然没有得到很好的理解。作为这项基础研究的一部分，我们对它的理解得到了提高，这将影响到广泛的应用。例如，由于表面不稳定性在摩擦中的作用，这项研究将对接触移动软材料的工程应用产生积极影响。这也将导致更好地了解夹层梁复合材料的动力学，并改善冲击吸收器，减震系统，和新的软电子设备。除了研究目标，这个项目有一个重要的教育和推广的组成部分，将积极影响学生从K-12通过研究生水平，并将增加在STEM领域的代表性不足的学生的参与。这个多学科的合作项目的研究目标是调查在动态载荷下软材料表面不稳定性的启动和传播，使用组合的理论，计算和实验方法。将使用落塔、高速视频和激光超声测试方法的组合进行实验表征。动态表面不稳定性传播将采用非线性有限元技术进行分析和计算建模。这个项目将提供显着的智力贡献，回答开放的问题，包括：什么是启动传播的表面不稳定性的条件，以及他们如何传播？表面不稳定性的传播是如何导致材料失效的？如何控制表面不稳定性的传播？更一般地说，由于几乎没有调查传播表面不稳定性的动力学，这项调查将打开一类新的基于不稳定性的表面波，并提供了一个更好的理解动态现象在软材料。

When soft materials are compressed, their surface often spontaneously forms wrinkles, creases, ridges, or folds with periodic patterns. These patterns are called 'surface instabilities'. Over the past several years, there has been significant interest in understanding how surface instabilities form, as they are ubiquitous in biological systems and have found wide use in engineering applications ranging from microfabrication to soft robotics. However, nearly all of the past studies have focused on understanding how surface instabilities form under very slow compression, or have neglected the dynamics leading to this event. This award will investigate how surface instabilities form and propagate across the surface of the material as a result of fast compression or impacts. The speed of the event causing the instability is critical as it yields fundamentally unique phenomena, which are prevalent in most physical systems, but still not well understood. The improved understanding gained as part of this fundamental research will impact a broad range of applications. For example, because of the role of surface instabilities in friction, this research will positively affect engineering applications with moving soft materials in contact. It will also lead to improved understanding of the dynamics of sandwich beam composites, and to improved impact absorbers, shock protective systems, and novel soft electronics devices. In addition to the research goals, this project has a significant education and outreach component that will positively affect students from K-12 through graduate levels, and will increase the involvement of underrepresented students in STEM fields.The research objective of this multidisciplinary, collaborative project is to investigate the initiation and propagation of surface instabilities in soft materials under dynamic loading, using a combined theoretical, computational, and experimental approach. Experimental characterization will be conducted using a combination of drop tower, high-speed video, and laser ultrasonic test methods. Dynamic surface instability propagation will be modeled analytically, and computationally using nonlinear finite element techniques. This project will provide significant intellectual contribution by answering open questions including: What are the conditions for initiating the propagation of surface instabilities, and how do they propagate? How does the propagation of surface instabilities lead to material failure? And how can the propagation of surface instabilities be manipulated? More generally, as there have been almost no investigations into the dynamics of propagating surface instabilities, this investigation will open a new class of instability-based surface waves and provide an improved understanding of dynamic phenomena in soft materials.