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

弹性体和其他软有机固体中的断裂成核和断裂扩展现象长期以来一直吸引着不同学科的众多研究人员的兴趣。虽然在对这两种现象的基本定性认识方面取得了一些进展，但进展是相互独立的，但缺乏一种统一的定量认识，将这两种现象联系起来。在这种情况下，该奖项支持在理论和实验分析上的研究合作，即断裂如何在弹性体中成核、传播和可能的自愈合，这些弹性体受到任意大的变形。除了解决一个几十年来一直悬而未决的基本科学问题外，这项研究所寻求的知识对于推动广泛的技术和医学发展至关重要。例如，该项目的结果将直接洞察：轮胎的失效、更强粘合剂的设计、骨组织的破裂、软骨的设计、伤口愈合的建模等。此外，该项目将培养两名研究生在学术界或工业界的职业生涯，并将在伊利诺伊大学厄巴纳-尚潘和德克萨斯大学奥斯汀分校。PI还将开展活动，通过创建课程模块和实验室演示，促进高中生在STEM课程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：i）在高时空分辨率下进行实验，该实验产生关于在三种具有实际意义的弹性体中的内部裂缝成核和扩展以及愈合的定量测量，以及ii）构建和数值实现连续统理论，该连续统理论在实验的直接指导下，描述，解释，并预测了在弹性体经历任意大的粘弹性变形时断裂的成核和扩展以及愈合。实验部分需要开发新的实验，利用光学显微镜和高速成像技术，以前所未有的1微米和200微秒的时空分辨率捕捉和测量各种基本过程的演变。另一方面，理论部分涉及一种新的数学公式和相关的数值实现，其将骨折和愈合以统一的方式视为相变，并且通过设计允许对各种潜在机制进行核算（通过弹性变形储存能量和通过粘性变形耗散能量以及产生新的表面），该奖项反映了NSF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.