Ju Jianzhu, Sanoja Gabriel E, Cipelletti Luca, Ciccotti Matteo, Zhu Bangguo, Narita Tetsuharu, Yuen Hui Chung, Creton Costantino
Sciences et Ingénierie de la Matière Molle, CNRS UMR 7615, École supérieure de physique et de chimie industrielles de la Ville de Paris, Sorbonne Université, Paris Sciences et Lettres Université, Paris 75005, France.
McKetta Department of Chemical Engineering, The University of Texas at Austin, Austin, TX 78723.
Proc Natl Acad Sci U S A. 2024 Nov 5;121(45):e2410515121. doi: 10.1073/pnas.2410515121. Epub 2024 Oct 30.
Tough soft materials such as multiple network elastomers (MNE) or filled elastomers are typically stretchable and include significant energy dissipation mechanisms that prevent or delay crack growth. Yet most studies and fracture models focus on steady-state propagation and damage is assumed to be decoupled from the local stress and strain fields near the crack tip. We report an in situ spatial-temporally resolved 3D measurement of molecular damage in mechanophore-labeled MNE just before a crack propagates. This technique, complemented by digital image correlation, allows us to compare the spatial distribution of both damage and deformation in single network (SN) elastomers and in MNE. Compared to SN, MNE have a wide-spread damage in front of the crack and, surprisingly, delocalize strain concentration. A continuum model, where damage distribution is fully coupled to the crack tip fields, is proposed to explain these results. Additional measurements of time-dependent molecular damage during fixed grips relaxation in the presence of a crack reveal that the less localized damage distribution delays fracture initiation. The observations and exploratory modeling reveal the dynamic fracture mechanism of MNE, providing guidance for rational design of high-performance tough elastomers.
诸如多重网络弹性体（MNE）或填充弹性体之类的坚韧软材料通常具有可拉伸性，并包含显著的能量耗散机制，可防止或延迟裂纹扩展。然而，大多数研究和断裂模型都集中在稳态扩展上，并且假定损伤与裂纹尖端附近的局部应力和应变场解耦。我们报告了在裂纹扩展之前对机械力敏染料标记的MNE中分子损伤进行的原位时空分辨三维测量。这项技术辅以数字图像相关技术，使我们能够比较单网络（SN）弹性体和MNE中损伤和变形的空间分布。与SN相比，MNE在裂纹前方有广泛的损伤，而且令人惊讶的是，应变集中发生了离域。提出了一个连续介质模型，其中损伤分布与裂纹尖端场完全耦合，以解释这些结果。在存在裂纹的情况下，对固定夹具松弛过程中随时间变化的分子损伤进行的额外测量表明，损伤分布的局部性越低，断裂起始的延迟就越大。这些观察结果和探索性建模揭示了MNE的动态断裂机制，为高性能坚韧弹性体的合理设计提供了指导。
