Fatigue-resistant polymer networks

Toughness of natural rubber measured under monotonic load is ~10,000 J/m2.

Fatigue threshold of natural rubber measured under cyclic load is ~50 J/m2.

The large difference is due to dissipation in the bulk.

@EnduricaWill @aljcrosby

Where does the threshold of 50 J/m2 come from? Lake-Thomas 1967 model.

Before a polymer chain breaks, every monomer of the chain is stretched near breaking.

When the chain snaps, only one bond breaks, but the energy of the entire chain is dissipated.

https://doi.org/10.1098/rspa.1967.0160

Stiffness-threshold conflict and a resolution.

High fatigue threshold requires a polymer network to have a long chain, but a network of long chains has low stiffness.

This paper describes a resolution of this conflict.

@DRudolfKing @CretonCost

https://doi.org/10.1115/1.4044897

The Lake-Thomas model exemplifies a general concept: elastic dissipater.

A structural unit is elastically stretched.

When the unit breaks, the energy of the entire unit dissipates.

An elastic dissipater reaches a fatigue threshold above 1000 J/m2.

https://doi.org/10.1016/j.mattod.2019.08.009

This idea of elastic dissipater has been used to make fatigue-resistant elastomers

https://doi.org/10.1016/j.jmps.2019.103751

@RobibAllarini @ykutsovsky

Elastic dissipater enables an elastomer to have both high toughness and low hysteresis. https://doi.org/10.1073/pnas.1821420116

Here is a review on fatigue of hydrogels.

@RuobingB @DrJiaweiYang

https://doi.org/10.1016/j.euromechsol.2018.12.001

Here is an iMechanica ( @iMechanica2006) Journal Club led by @lin_shaoting and @ProfZhaoMIT on fatigue-resistant hydrogels.

https://imechanica.org/node/24333 

This paper shows that tough hydrogel adhesion is susceptible to fatigue.

https://doi.org/10.1016/j.eml.2019.100601

@Ljycanon @chenchao04

This paper shows that long-chain network adhesion has high fatigue threshold.

https://doi.org/10.1016/j.eml.2020.100813

@HangYan95173747 @Baohong_Chen @EnduricaWill @CretonCost

In getting ready for a graduate course, I add a crosslink between this thread and an iMechaanica thread on hydrogel fatigue.

https://imechanica.org/node/23127 

Please add ideas and links.

@RuobingB @DrJiaweiYang @ProfZhaoMIT @lin_shaoting @CretonCost @EnduricaWill @jasongsteck @ToLiTeng