CAREER: Fracture Mechanics of Soft Dissipative Materials

该学院早期职业发展计划（Career）奖将支持软弹性体和水凝胶抗断裂性的基础研究。可以承受大可逆变形的软材料已广泛应用于工业应用，如轮胎和软胶粘剂，或新兴技术，如软机器人，生物医学植入物和可拉伸显示器。在这些应用中，底层软质材料需要具有可拉伸性，以实现功能，同时耐断裂，以提高可靠性。在这种需求的驱动下，各种物理或化学机制被开发出来以增强软材料的抗断裂性，它们有一个共同的主题：在变形过程中引入材料的能量耗散或消耗。然而，由于缺乏对能量耗散与断裂阻力之间定量关系的理解，这种软耗散材料的断裂理论建模和实验表征具有挑战性。该研究项目将建立实验和建模能力，以揭示与软材料断裂相关的复杂非线性力学，这将为工程上具有机械鲁棒性的新型软功能材料提供定量原理，以及测量和预测软材料断裂的新工具。从而促进软材料断裂科学的发展，促进国家的健康、繁荣和福祉。作为研究的一部分，将开发教育和推广项目，通过创建跨学科的夏季研讨会，将研究成果整合到课程和K-12推广活动中，并与工业伙伴建立合作关系，促进学术、教育和工业部门对软材料断裂的研究。软材料断裂面临的主要挑战是裂纹尖端附近的大变形，这种变形会导致非线性应变场和应力场以及复杂的破坏和耗散行为。为了解决这一挑战，我们将采用颗粒跟踪方法来测量模型软质材料在不同断裂模式下的裂纹尖端变形场。对于弹性材料，实验将提供数据来评估现有裂纹尖端渐近解的有效区域，发现裂纹尖端场的新结构，并通过j积分来局部评估能量释放率，从而消除对专门实验几何的要求。对于耗散材料，将利用裂纹尖端变形场的实验数据，结合精确的本构模型，识别裂纹尖端耗散区，并分别测量其本征韧性和耗散韧性。本文还将建立一个有限元模型，将以内聚区为代表的裂纹尖端破坏过程与体材料耗散相耦合，从而能够预测软耗散材料中的裂纹扩展。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。

This Faculty Early Career Development Program (CAREER) award will support fundamental research on the fracture resistance of soft elastomers and hydrogels. Soft materials that can undergo large reversible deformation have been widely utilized in industrial applications such as tires and soft adhesives, or emerging technologies such as soft robots, biomedical implants and stretchable display. In these applications, the underlying soft materials are required to be stretchable to enable functionality and yet fracture resistant to enhance reliability. Driven by this need, various physical or chemical mechanisms have been developed to enhance the fracture resistance of soft materials, and they share a common theme: to introduce energy dissipation or consumption by the material during deformation. However, theoretical modeling and experimental characterization of fracture in such soft dissipative materials are challenging due to the lack of understandings on the quantitative relation between energy dissipation and fracture resistance. This research program will establish experimental and modeling capabilities to uncover the complex nonlinear mechanics associated with soft material fracture, which will lead to quantitative principles for engineering new soft functional materials that are mechanically robust, as well as new tools to measure and predict fracture in soft materials. Thus, the research will promote the science of soft material fracture to advance the national health, prosperity, and welfare. As part of research, education and outreach programs will be developed to promote research of soft material fracture in academic, educational and industrial sectors by creating an interdisciplinary summer workshop, integrating research findings into curriculum and K-12 outreach activities, and building collaborations with industrial partners.A major challenge in soft material fracture is the large deformation near the tip of a crack, which causes nonlinear strain and stress fields as well as complex failure and dissipation behaviors. To address this challenge, a particle tracking method will be used to measure the crack tip deformation field in model soft materials under various fracture modes. For elastic materials, the experiments will provide data to assess the region of validity for existing crack tip asymptotic solutions, to discover new structures of crack tip fields, and to enable local evaluation of energy release rate through the J-integral, thus eliminating the requirement of specialized experimental geometries. For dissipative materials, the experimental data of crack tip deformation field, augmented by accurate constitutive models, will be used to identify the crack tip dissipation zone and to separately measure the intrinsic and dissipative toughness. A finite element model will also be developed to couple the crack tip failure process, represented by a cohesive zone, with the bulk material dissipation, which will enable the prediction of crack growth in soft dissipative materials.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.