The phenomena of how fractures begin (nucleate) and grow (propagate) in elastomers and other soft organic solids have long occupied the interest of numerous investigators across different disciplines. While initial progress has been made in the basic qualitative understanding of both, there is a lack of a quantitative and unified understanding that bridges the two phenomena. In this context, this award supports a research collaboration on the theoretical and experimental analysis of how fracture nucleates, propagates, and possibly self-heals in elastomers subjected to arbitrarily large deformations. In addition to addressing a fundamental scientific question that has remained open for decades, the knowledge sought by this research is essential for the advancement of a broad range of technologies and medical prognoses. For instance, the results from this project will provide direct insight into: the failure of tires, the design of stronger adhesives, the rupture of aneurisms, the design of cartilage, modeling of wound healing, etc. Additionally, this project will train two graduate students for careers in academia or industry and will integrate research results in the undergraduate and graduate curricula at the University of Illinois Urbana-Champaign and the University of Texas at Austin. The PIs will also carry out activities to promote interest in high school students to pursue higher education and careers in STEM programs, especially in the field of mechanics, through the creation of lesson modules and laboratory demonstrations.
The main objective of this project is two-fold: i) to carry out experiments at high spatiotemporal resolution that produce quantitative measurements concerning internal fracture nucleation and propagation, as well as healing, in three elastomers of practical significance, and ii) to construct and numerically implement a continuum theory that, with direct guidance from the experiments, describes, explains, and predicts the nucleation and propagation of fracture, and healing in elastomers undergoing arbitrarily large viscoelastic deformations. The experimental component entails the development of new experiments that will leverage the use of optical microscopy and high-speed imaging in order to capture and measure the evolution of the various underlying processes at an unprecedented spatiotemporal resolution of 1 micron and 200 microseconds. On the other hand, the theoretical component involves a novel mathematical formulation, and associated numerical implementation, that views fracture and healing in a unified manner as a phase transition and that allows, by design, for the accounting of the various underlying mechanisms (storage of energy by elastic deformation and dissipation of energy by viscous deformation and the creation of new surfaces) in a clear, natural, and theoretically consistent manner.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
