Biaxial Loading Effects on Strain Energy Release Rate and Crack-Tip Strain Field in Elastic Hydrogels

• Published in: Macromolecules Vol. 54; no. 10; pp. 4792 - 4801
• Main Authors: Mai, Thanh-Tam, Urayama, Kenji
• Format: Journal Article
• Language: English
• Published: American Chemical Society 25.05.2021
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/acs.macromol.1c00445

We characterized the strain energy release rate and local crack-tip strain field for elastic hydrogels under several types of biaxial loading: planar, unequal biaxial, and equibiaxial extensions. The strain energy release rate (G) in each type of biaxial strain is characterized via two different approaches. One evaluates G from the change in strain energy with respect to the notch length (X c) using single-edge notched specimens with various X c values. The other estimates G from the difference in strain energy density between the two regions far behind and ahead of the crack tip. The excellent agreement between the G values obtained by the two methods demonstrated their reliability. We also revealed the features of the local crack-tip strain field in biaxial loading, including crack-tip opening displacement, strain field area, strain magnitude resulting from crack opening, and strain singularity exponent for strain growth near the crack tip. Importantly, these properties are governed exclusively by G, independent of the biaxial loading type. The results provide an important basis for a comprehensive understanding of the fracture behavior of elastic soft materials under complicated deformations.