Uniaxial compression constitutive equations for saturated hydrogel combined water-expelled behavior with environmental factors and the size effect

For soft materials with high water content under compression loading, their water-expelled behavior leads to volume changes and should be considered in constitutive equations. In this study, uniaxial compression experiments are conducted for saturated hydrogels of different sizes in different environments. Furthermore, the constitutive equations of uniaxial compression combined water-expelled behavior considering environmental factors and the size effect were derived, which may describe the experimental results well and reveal the mechanism of the difference in mechanical behavior of hydrogels in different environments and different sizes. Our work has important reference value for characterizing the mechanical behavior of biological soft matter.