Microstructure and full-field deformation measurement of compound porous hydrogels using digital speckle correlation method

The micro-morphologies of porous poly(vinyl alcohol) (PVA) hydrogel with different porous structures were observed. The digital speckle correlation method (DSCM) connected with mechanical properties test was used to investigate the deformation of porous hydrogel. The deformation of micro-fields, compressive modulus and Poisson's ratio of porous hydrogel were compared under different compressive loads. The pore size and porosity of different structures significantly affect the distribution of iso-displacement lines. It is revealed that the iso-displacement lines are equality and approximately parallel in hydrogels with unconnected porous structure, but are tortuous and S like in hydrogels with connected porous structure. The field, in which the iso-displacement lines are intensive, is the area of stress concentration. The deformation is increased with adding porosity. The Poisson's ratio of hydrogel is decreased with increasing of load and content of porogen. The compression modulus is increased with increasing of the strain.