School of Civil Engineering and Transportation, South China University of Technology, No.381, Wushan Road, Guangzhou, Guangdong, China; Guangdong Institute of Intelligent Manufacturing, Guangzhou, China.
School of Civil Engineering and Transportation, South China University of Technology, No.381, Wushan Road, Guangzhou, Guangdong, China.
J Mech Behav Biomed Mater. 2018 Sep;85:181-187. doi: 10.1016/j.jmbbm.2018.06.004. Epub 2018 Jun 5.
For high-water content hydrogels in compression, the water inside of hydrogels contributes to the response of hydrogels to external loads directly, but part of the water is expelled from hydrogels in the meantime to change the volume of the hydrogel and reduce the contribution. In order to consider the contribution of the water in the constitution equation, PVA (polyvinyl alcohol) hydrogels with high-water content were used as examples, and compressive experiments were carried out to measure both the stress-strain relation and the change of the volume in the meantime. By considering the effect of the difference of the contribution of water in different directions of the hydrogel, we deduced a new constitutive equation, which can pretty well depict the stress-strain of hydrogels with different water contents. The results showed that the contribution of water to the total stress increases with the compression strain and even exceed that of the polymer, although the expelled water reduces the contribution at the early loading stage, which well explains the difference of elastic moduli of hydrogels in compression and tension.
对于高含水量水凝胶在压缩过程中，水凝胶内部直接有助于水凝胶对外部负载的响应，但同时部分水凝胶中的水被挤出，以改变水凝胶的体积并降低贡献。为了在本构方程中考虑水的贡献，以高含水量的 PVA（聚乙烯醇）水凝胶为例，同时进行压缩实验以测量应力-应变关系和体积的变化。通过考虑水在水凝胶不同方向上的贡献差异的影响，我们推导出了一个新的本构方程，该方程可以很好地描述具有不同含水量的水凝胶的应力-应变关系。结果表明，尽管在早期加载阶段挤出的水会降低贡献，但水对总应力的贡献随着压缩应变的增加而增加，甚至超过了聚合物的贡献，这很好地解释了水凝胶在压缩和拉伸时弹性模量的差异。
