Fatigue Fracture of Self-Recovery Hydrogels

Dear Colleagues,

Here is our recent paper “Fatigue Fracture of Self-Recovery Hydrogels”. To the hydrogel community, this paper distinguishes the fatigue fracture and the self-recovery of a hydrogel. To the mechanics community, we show that, for the first time in hydrogels, the fatigue threshold depends only on the covalent network, but not on the noncovalent interactions that provide dissipation.

https://pubs.acs.org/doi/abs/10.1021/acsmacrolett.8b00045?journalCode=am...

Fatigue Fracture of Self-Recovery Hydrogels

Ruobing Bai, Jiawei Yang, Xavier P. Morelle, Canhui Yang, and Zhigang Suo

Abstract:

Hydrogels of superior mechanical behavior are under intense development for many applications. Some of these hydrogels can recover their stress–stretch curves after many loading cycles. These hydrogels are called self-recovery hydrogels or even fatigue-free hydrogels. Such a hydrogel typically contains a covalent polymer network, together with some noncovalent, reversible interactions. Here we show that self-recovery hydrogels are still susceptible to fatigue fracture. We study a hydrogel containing both covalently cross-linked polyacrylamide and un-cross-linked poly(vinyl alcohol). For a sample without precut crack, the stress–stretch curve recovers after thousands of loading cycles. For a sample with a precut crack, however, the crack extends cycle by cycle. The threshold for fatigue fracture depends on the covalent network but negligibly on noncovalent interactions. Above the threshold, the noncovalent interactions slow down the extension of the crack under cyclic loads.