Fatigue fracture of tough hydrogels

Bai, Ruobing; Yang, Quansan; Tang, Jing-Shi; Morelle, Xavier; Vlassak, Joost J.; Suo, Zhigang

doi:10.1016/j.eml.2017.07.002

Cited by 231 publications

(204 citation statements)

References 56 publications

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“…This is consistent with the higher tan δ of semi‐IPN hydrogel, that is, higher energy dissipation efficiency. In comparison, the stress and the toughness of the IPN hydrogel of G25‐SA6 were much higher, and they decreased much more after the first compressing run, and then decreased gradually, similar as those reported in literature . The much higher strength and toughness of the IPN hydrogel should be contributed from the higher chain density and from the sacrificial ionic crosslinkings.…”

Section: Resultssupporting

confidence: 86%

“…It has been suggested that there are some microstructure changes including disentanglements and sliding of polymer chains during the energy dissipation process, which results in decrease in strength of hydrogel . Therefore, the hydrogels were, respectively, compressed to 50% strain and to higher stain of 75%, and then recovered naturally to zero stress.…”

Section: Resultsmentioning

confidence: 99%

“…The higher strengthening and toughening effect brought by the IPN structure has been carefully analyzed. For practical application, hydrogel is often subjected to cyclic stress, so that the stability of hydrogel is very important . Therefore, cyclic loading and unloading of the hydrogels were carried out.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Mechanical Strengths of Hydrogels of Poly(N,N‐Dimethylacrylamide)/Alginate with IPN and of Poly(N,N‐Dimethylacrylamide)/Chitosan with Semi‐IPN Microstructures

Bai

Huang

Xiao

et al. 2019

Macro Materials & Eng

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Tough hydrogels receive continuous attention because of their promising applications in many fields. Herein, tough hydrogels of poly (N,N‐dimethylacrylamide) (PDMAA)/alginate (SA) are prepared, with interpenetrating network (IPN) and of PDMAA/chitosan (CS) with semi‐IPN microstructure, respectively. The toughening of the hydrogel by incorporating natural polymers is studied by compressing tests and dynamic mechanical analyses. Moreover, cyclic load–unload compressing of the two types of hydrogels are performed at low strains and under relatively high strains, in order to compare their strength and anti‐fatigue properties. The results indicate that the mechanical strength can be markedly improved upon addition of the natural polymers, and the IPN hydrogel of PDMAA/SA reveals much higher mechanical performances but is less stable. However, the semi‐IPN hydrogel of PDMAA/CS displays excellent anti‐fatigue stability, but with relatively low strength. Swelling tests, scanning electron microscopy, and Fourier transform infrared spectroscopy are carried out to study the microstructures of the hydrogels, which are carefully analyzed to understand the difference in mechanical performances of those hydrogels. The results suggest that the presence of sacrificial unit and higher chain density in the IPN are helpful for toughening hydrogels, while the semi‐IPN network is beneficial to improve the energy dissipation efficiency.

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Section: Resultssupporting

confidence: 86%

Section: Resultsmentioning

confidence: 99%

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Mechanical Strengths of Hydrogels of Poly(N,N‐Dimethylacrylamide)/Alginate with IPN and of Poly(N,N‐Dimethylacrylamide)/Chitosan with Semi‐IPN Microstructures

Bai

Huang

Xiao

et al. 2019

Macro Materials & Eng

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“…[ 4,59,60 ] It is impossible to extract information on a hydrogel's fatigue resistance from single stress amplitude tests, stopped at arbitrary cycle numbers, though many studies have focused on this analysis. [40–42, 61–66 ] An overarching goal of this work is to understand the tensile fatigue properties of PVA with and without additives. To the author's knowledge, no such study focusing on full‐load spectrum cyclic, tensile testing has been published for a high‐strength synthetic hydrogel.…”

Section: Introduction Of Synthetic Hydrogelsmentioning

confidence: 99%

Tensile Fatigue of Poly(Vinyl Alcohol) Hydrogels with Bio‐Friendly Toughening Agents

Koshut

Smoot

Rummel

et al. 2020

Macro Materials & Eng

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Inspired by the avoidance of toxic chemical crosslinkers and harsh reaction conditions, this work describes a poly(vinyl alcohol)‐based (PVA) double‐network (DN) hydrogel aimed at maintaining biocompatibility through the combined use of bio‐friendly additives and freezing–thawing cyclic processing for the application of synthetic soft‐polymer implants. This DN hydrogel is studied using techniques that characterize both its chemical and mechanical behavior. A variety of bio‐friendly additives are screened for their effectiveness at improving the toughness of the PVA hydrogel system in monotonic tension. Starch is selected as the best additive for further tensile testing as it brings about a near 30% increase in ultimate tensile strength and maintains ease of processing. This PVA–starch DN sample is then studied for its tensile fatigue properties through cyclic, strain‐controlled testing to develop a fatigue life curve. Though an increase in monotonic tensile strength is observed, the PVA–starch DN hydrogel does not bring about an improvement in the fatigue behavior as compared to the control. Although synthetic hydrogel reinforcement is widely researched, this work presents the first fatigue analysis of its kind and it is intended to serve as a guide for future fatigue studies of reinforced hydrogels.

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“…The energy dissipation is large when the hydrogel is loaded for the first time, but is often poorly reversible in the subsequent loading cycles, due to the irreversible nature of the bonds (e.g., covalent bonds), or the relatively short time allowed for recovery of the bonds (e.g., most mechanical motions work with periods shorter than a few minutes). Ultimately, all hydrogels suffer fatigue fracture, that is, the gradual extension of crack from an initial flaw under cyclic loads . The highest threshold for fatigue fracture of a double‐network, tough hydrogel reported up‐to‐date is about 400 J m −2 , still only 1/10 of its bulk fracture toughness …”

mentioning

confidence: 99%

Flaw‐Insensitive Hydrogels under Static and Cyclic Loads

Bai

Yang

Morelle

et al. 2019

Macromol. Rapid Commun.

Self Cite

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New applications of hydrogels draw growing attention to the development of tough hydrogels. Most tough hydrogels are designed through incorporating large energy dissipation from breaking sacrificial bonds. However, these hydrogels still fracture under prolonged cyclic loads with the presence of even small flaws. This paper presents a principle of flaw‐insensitive hydrogels under both static and cyclic loads. The design aligns the polymer chains in a hydrogel at the molecular level to deflect a crack. To demonstrate this principle, a hydrogel of polyacrylamide and polyvinyl alcohol is prepared with aligned crystalline domains. When the hydrogel is stretched in the direction of alignment, an initial flaw deflects, propagates along the loading direction, peels off the material, and leaves the hydrogel flawless again. The hydrogel is insensitive to pre‐existing flaws, even under more than ten thousand loading cycles. The critical degree of anisotropy to achieve crack deflection is quantified by experiments and fracture mechanics. The principle can be generalized to other hydrogel systems.

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Fatigue fracture of tough hydrogels

Cited by 231 publications

References 56 publications

Mechanical Strengths of Hydrogels of Poly(N,N‐Dimethylacrylamide)/Alginate with IPN and of Poly(N,N‐Dimethylacrylamide)/Chitosan with Semi‐IPN Microstructures

Mechanical Strengths of Hydrogels of Poly(N,N‐Dimethylacrylamide)/Alginate with IPN and of Poly(N,N‐Dimethylacrylamide)/Chitosan with Semi‐IPN Microstructures

Tensile Fatigue of Poly(Vinyl Alcohol) Hydrogels with Bio‐Friendly Toughening Agents

Flaw‐Insensitive Hydrogels under Static and Cyclic Loads

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