Effect of the shape of hydrogel samples on their stretch‐fracture properties

Abstract

Hydrogels have broad application prospects, but the measurement of their mechanical properties often lacks stability. This study investigates the mechanical properties of hydrogels, with a specific focus on the influence of sample geometry on the tensile‐fracture testing results. In the process of stretching the hydrogel along its length, increasing the width and thickness will result in uneven stress distribution. When the width of PAM hydrogel is three times that of initial sample (5 mm of width), the elastic modulus, maximum stress, and maximum strain of PAM hydrogel are reduced by about 16.8%, 69.2%, and 26.5%, respectively. Similarly, compared to the initial sample (1 mm of thickness), the elastic modulus of the triple thickness sample was reduced by about 6.5%, the maximum stress was reduced by 31%, and the maximum strain was reduced by 18.3%. In contrast, increasing the length of the hydrogel can improve the tensile properties of the hydrogel. Finite element calculations support these findings that the size increase in the loading direction improves the stress dispersion uniformity. These results indicate that the shape (length, width and thickness) of the hydrogel sample affects the tensile properties of the hydrogel and should be paid attention in related studies.