InSIS Webinar Series – 2023 – Crack propagation in soft materials

Abstract:

Soft materials in everyday uses such as jellies, creams, and elastomers are ubiquitous; and are also attractive as tissue engineering and drug eluting scaffolds, where, they generally undergo large nonlinear deformations. Tuneability in mechanical properties present distinct advantages in the use of such materials, whereas, low toughness and brittle fractures restrict their use in load bearing applications. I will discuss the recent work from my laboratory in the fracture characterization of model biomimetic hydrogels with differential crosslinks using cavitation rheology. In this method, we measure the dynamic changes in pressure during bubble inflation to quantify the fracture toughness of the hydrogel. Our results show that the material nonlinearity and strain rate effects limit the use of cavitation rheology in the quantification of material toughness. Bubble growth is spheroidal in soft gels, whereas, highly cross-linked gels have ellipsoidal shapes during inflation. We also fabricate hydrogels with similar storage moduli but differing in their loss moduli to establish the importance of the surface energy term in symmetry breaking shape transitions during bubble inflation. Finally, we use pure shear notch tests to demonstrate that crack propagation in soft hydrogels begins when the tip curvatures are lowest. Such studies make fracture characterization in soft materials fascinating and challenging from both experimental and theoretical perspectives.

Bio-data of speaker:

Namrata Gundiah is a Professor of Mechanical Engineering at the Indian Institute of Science, Bangalore. Her research interests are broadly in nonlinear tissue mechanics, cell mechano-biology, and failures in biological materials and hydrogels. Prior to joining the Institute, she worked as a postdoctoral fellow at the University of California, San Francisco where she collaborated with cardiac surgeons. She earned an M.S. and Ph.D. in Mechanical Engineering from the University of California, Berkeley in 2004. Namrata has been awarded the Ramanujan fellowship and the Constance Tipper silver medal from the International Congress on Fracture, and is on the editorial board of Biomechanics and Modeling in Mechano-biology, and Cell Adhesion and Migration journals. She also serves as the founding Chair of the Office of Research Grants at IISc.

Organized by:

InSIS and Center for Structural Integrity of Safety Critical Systems, IIT Madras