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

长期以来，弹性体和其他软有机固体中的裂缝如何开始(成核)和生长(扩展)的现象一直吸引着不同学科的许多研究人员的兴趣。虽然在对这两种现象的基本定性理解方面取得了初步进展，但缺乏将这两种现象联系起来的定量和统一的理解。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如何成核、扩展以及可能的自我修复的理论和实验分析的研究合作。除了解决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进广泛的技术和医学预测至关重要。例如，这个项目的结果将提供对轮胎失效、更坚固的粘合剂的设计、动脉瘤的破裂、软骨的设计、伤口愈合的模型等的直接洞察。此外，该项目将培养两名在学术界或工业领域就业的研究生，并将把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。PIS还将开展活动，通过创建课程单元和实验室演示，促进高中生在STEM方案中接受高等教育和从事职业，特别是在机械领域。这个项目的主要目标有两个：i)在高时空分辨率下进行实验，在三个具有实际意义的弹性体中对内部裂纹的形核和扩展以及愈合进行定量测量，以及ii)构建和数值实现一个连续介质理论，该理论在实验的直接指导下描述、解释和预测任意大的粘弹性变形的弹性体中的裂纹的形核和扩展以及愈合。实验部分需要开发新的实验，利用光学显微镜和高速成像，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，该公式将统一方式的骨折和愈合视为相变，并允许通过设计以明确、自然和理论上一致的方式解释各种基本机制(通过弹性变形存储能量和通过粘性变形耗散能量)。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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 how fractures begin (nucleate) and grow (propagate) in elastomers and other soft organic solids have long occupied the interest of numerous investigators across different disciplines. While initial 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.