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

当软材料被压缩时，其表面经常自发地形成具有周期性图案的皱纹、折痕、脊或褶皱。这些图案被称为“表面不稳定性”。在过去的几年里，人们对了解表面不稳定性是如何形成的非常感兴趣，因为它们在生物系统中普遍存在，并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，过去几乎所有的研究都集中在了解表面不稳定性是如何在非常缓慢的压缩下形成的，或者忽略了导致这一事件的动力学。该奖项将调查由于快速压缩或冲击，表面不稳定性是如何形成并在材料表面传播的。导致不稳定的事件的速度是至关重要的，因为它产生了基本独特的现象，这些现象在大多数物理系统中很普遍，但仍然没有被很好地理解。作为这项基础研究的一部分而获得的更好的理解将对广泛的应用产生影响。例如，由于表面不稳定性在摩擦中的作用，这项研究将对移动软材料接触的工程应用产生积极的影响。它还将有助于更好地理解夹层梁复合材料的动力学，并改进冲击减振器、防震系统和新型软电子设备。除了研究目标之外，这个项目还有一个重要的教育和推广部分，将对从K-12到研究生水平的学生产生积极的影响，并将增加STEM领域中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利用理论、计算和实验相结合的方法，研究动态载荷下软材料中表面不稳定性的启动和传播。实验表征将使用落塔、高速视频和激光超声测试方法的组合进行。将使用非线性有限元技术对动态表面不稳定性的传播进行解析建模和计算。这个项目将通过回答开放的问题提供重大的智力贡献，包括：启动表面不稳定性传播的条件是什么，它们是如何传播的？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？更广泛地说，由于几乎没有关于表面不稳定性传播动力学的研究，这项研究将开启一类新的基于不稳定性的表面波，并提供对软材料中动力学现象的更好的理解。

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.