Collaborative Research: Fracture and Healing of Elastomers: An Experimental and Theoretical Investigation at High Spatiotemporal Resolution

弹性体和其他软质有机固体中的断裂成核和断裂扩展现象长期以来一直引起不同学科众多研究者的兴趣。虽然在对这两种现象的基本定性认识方面取得了一些但各不相同的进展，但仍缺乏将这两种现象联系起来的定量和统一的认识。在此背景下，该奖项支持了一项关于弹性体在任意大变形下裂缝如何成核、扩展和可能自愈的理论和实验分析的研究合作。除了解决一个几十年来一直开放的基本科学问题外，这项研究所寻求的知识对于广泛的技术进步和医学预后至关重要。例如，这个项目的结果将提供直接的见解：轮胎的失效，更强的粘合剂的设计，动脉瘤的破裂，软骨的设计，伤口愈合的建模等。此外，该项目将培训两名研究生从事学术界或工业界的职业，并将研究成果整合到伊利诺伊大学厄巴纳-香槟分校和德克萨斯大学奥斯汀分校的本科和研究生课程中。pi还将开展活动，通过创建课程模块和实验室演示，提高高中生在STEM项目中接受高等教育和职业的兴趣，特别是在力学领域。该项目的主要目标有两个：1)在高时空分辨率下进行实验，对三种具有实际意义的弹性体进行内部断裂成核、扩展和愈合的定量测量；2)构建并数值实现连续统理论，该理论在实验的直接指导下，描述、解释和预测任意大粘弹性变形弹性体的断裂成核、扩展和愈合。实验部分需要开发新的实验，这些实验将利用光学显微镜和高速成像技术，以前所未有的1微米200微秒的时空分辨率捕捉和测量各种潜在过程的演变。另一方面，理论部分涉及一个新颖的数学公式，以及相关的数值实现，它将骨折和愈合以统一的方式视为相变，并且通过设计，允许以清晰，自然和理论上一致的方式计算各种潜在机制（通过弹性变形存储能量，通过粘性变形耗散能量和创造新表面）。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The phenomena of fracture nucleation and fracture propagation in elastomers and other soft organic solids have long occupied the interest of numerous investigators across different disciplines. While some but separate progress has been made in the basic qualitative understanding of both, there is a lack of a quantitative and unified understanding that bridges the two phenomena. In this context, this award supports a research collaboration on the theoretical and experimental analysis of how fracture nucleates, propagates, and possibly self-heals in elastomers subjected to arbitrarily large deformations. In addition to addressing a fundamental scientific question that has remained open for decades, the knowledge sought by this research is essential for the advancement of a broad range of technologies and medical prognoses. For instance, the results from this project will provide direct insight into: the failure of tires, the design of stronger adhesives, the rupture of aneurisms, the design of cartilage, modeling of wound healing, etc. Additionally, this project will train two graduate students for careers in academia or industry and will integrate research results in the undergraduate and graduate curricula at the University of Illinois Urbana-Champaign and the University of Texas at Austin. The PIs will also carry out activities to promote interest in high school students to pursue higher education and careers in STEM programs, especially in the field of mechanics, through the creation of lesson modules and laboratory demonstrations. The main objective of this project is two-fold: i) to carry out experiments at high spatiotemporal resolution that produce quantitative measurements concerning internal fracture nucleation and propagation, as well as healing, in three elastomers of practical significance, and ii) to construct and numerically implement a continuum theory that, with direct guidance from the experiments, describes, explains, and predicts the nucleation and propagation of fracture, and healing in elastomers undergoing arbitrarily large viscoelastic deformations. The experimental component entails the development of new experiments that will leverage the use of optical microscopy and high-speed imaging in order to capture and measure the evolution of the various underlying processes at an unprecedented spatiotemporal resolution of 1 micron and 200 microseconds. On the other hand, the theoretical component involves a novel mathematical formulation, and associated numerical implementation, that views fracture and healing in a unified manner as a phase transition and that allows, by design, for the accounting of the various underlying mechanisms (storage of energy by elastic deformation and dissipation of energy by viscous deformation and the creation of new surfaces) in a clear, natural, and theoretically consistent manner.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.