Poroelastic fracture of polyacrylamide hydrogels: Enhanced crack tip swelling driven by chain scission

IF 5 2区工程技术 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY

Journal of The Mechanics and Physics of Solids Pub Date : 2024-11-12 DOI:10.1016/j.jmps.2024.105954

Qifang Zhang, Junjie Liu, Gang Zhang, Yuhong Li, Nan Hu, Jinglei Yang, Yan Yang, Shaoxing Qu, Qianhua Kan, Guozheng Kang

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引用次数: 0

Abstract

The deformation of hydrogels is accompanied by water migration, a process that plays a crucial role in their fracture behaviors. Previous investigations primarily focus on how the water migration between the environment and hydrogel affects the fracture of hydrogels. Herein, a novel mechanism of the rate-dependent fracture of hydrogels induced by interior water migration is uncovered. Notched polyacrylamide (PAAm) hydrogels are stretched at various stretch rates in both oil and deionized (DI) water environments. Notably, the critical stretches to crack propagation are positively correlated with the stretch rates in both the two environments. This rate-dependent fracture is attributed to the crack tip swelling of PAAm hydrogels. Delayed fracture tests conducted in oil further verify the co-existence of delayed fracture and rate-dependent fracture resulted from interior water migration in PAAm hydrogels. The experimental findings are interpreted by considering the imperfection of a real polymer network, in which the scission of short chains in the region neighboring the crack tip reduces the average crosslinking density locally, thereby greatly amplifying the degree of crack tip swelling and its influence on the fracture of hydrogels. A constitutive model coupling the evolution of polymer network and the diffusion of water molecules is proposed, which can predict the crack tip swelling of notched PAAm hydrogels through the finite element method. Assuming that the decrease in fracture toughness is positively related to the swelling along the crack propagation surface, the predicted normalized fracture toughness matches the experimental results of PAAm hydrogels stretched in water well, and satisfies those in oil environment qualitatively. This work highlights the significant influence of interior water migration on the fracture of hydrogels and provides insights that may guide the design of hydrogels with enhanced fracture resistance.

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聚丙烯酰胺水凝胶的气弹性断裂：由链裂解驱动的裂缝尖端膨胀增强

水凝胶的变形伴随着水迁移，这一过程对其断裂行为起着至关重要的作用。以往的研究主要集中于环境与水凝胶之间的水迁移如何影响水凝胶的断裂。本文揭示了内部水迁移诱导水凝胶速率依赖性断裂的新机制。缺口聚丙烯酰胺（PAAm）水凝胶在油和去离子水环境中以不同的拉伸速率拉伸。值得注意的是，在这两种环境中，裂纹扩展的临界拉伸与拉伸速率呈正相关。这种与速率相关的断裂归因于 PAAm 水凝胶的裂纹尖端膨胀。在油中进行的延迟断裂测试进一步验证了 PAAm 水凝胶内部水分迁移导致的延迟断裂和速率依赖性断裂的并存。考虑到真实聚合物网络的不完善性，对实验结果进行了解释，其中裂缝尖端附近区域的短链断裂降低了局部的平均交联密度，从而大大增加了裂缝尖端的膨胀程度及其对水凝胶断裂的影响。本文提出了聚合物网络演化与水分子扩散耦合的构效模型，可通过有限元方法预测缺口 PAAm 水凝胶的裂尖膨胀。假定断裂韧性的降低与沿裂纹扩展面的膨胀呈正相关，预测的归一化断裂韧性与水井中拉伸 PAAm 水凝胶的实验结果相吻合，并在定性上满足石油环境中的实验结果。这项研究强调了内部水迁移对水凝胶断裂的重要影响，并为设计抗断裂性能更强的水凝胶提供了指导。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Journal of The Mechanics and Physics of Solids 物理-材料科学：综合

CiteScore

9.80

自引率

9.40%

发文量

276

审稿时长

52 days

期刊介绍： The aim of Journal of The Mechanics and Physics of Solids is to publish research of the highest quality and of lasting significance on the mechanics of solids. The scope is broad, from fundamental concepts in mechanics to the analysis of novel phenomena and applications. Solids are interpreted broadly to include both hard and soft materials as well as natural and synthetic structures. The approach can be theoretical, experimental or computational.This research activity sits within engineering science and the allied areas of applied mathematics, materials science, bio-mechanics, applied physics, and geophysics. The Journal was founded in 1952 by Rodney Hill, who was its Editor-in-Chief until 1968. The topics of interest to the Journal evolve with developments in the subject but its basic ethos remains the same: to publish research of the highest quality relating to the mechanics of solids. Thus, emphasis is placed on the development of fundamental concepts of mechanics and novel applications of these concepts based on theoretical, experimental or computational approaches, drawing upon the various branches of engineering science and the allied areas within applied mathematics, materials science, structural engineering, applied physics, and geophysics. The main purpose of the Journal is to foster scientific understanding of the processes of deformation and mechanical failure of all solid materials, both technological and natural, and the connections between these processes and their underlying physical mechanisms. In this sense, the content of the Journal should reflect the current state of the discipline in analysis, experimental observation, and numerical simulation. In the interest of achieving this goal, authors are encouraged to consider the significance of their contributions for the field of mechanics and the implications of their results, in addition to describing the details of their work.