Wind farm propeller blade, heal thyself

Urbana (IL) - Researchers at the University of Illinois at Urbana-Champaign have developed a low-cost, active material which can repair tiny fractures it incurs. Researchers believe the material may be of significant benefit on applications ranging from airplane fuselages to wind-farm propeller blades, basically anything which is exposed to repeated stress and possible micro-fractures.

Previous substances which provided this kind of self-healing characteristics were expensive ruthenium-based Grubbs catalysts. The new mixture incorporates chlorobenzene microcapsules, about 150 microns in diameter each. When a crack forms it punctures the microcapsules, releasing a form of activating agent which moves out through the material looking for unreacted epoxy monomers.

The Murchison-Mallory Professor of Chemistry at Illinois, Jeffrey Moore, said "Self-healing of epoxy materials with encapsulated solvents can prevent further crack propagation, while recovering most of the material’s mechanical integrity." Laboratory tests have shown that as much as 82% of the original material strength remained after self-healing of fractures.

Right now the focus is on the cost savings of this solution, instead of the ruthenium-based solution. "By removing the catalyst from our material system, we now have a simpler and more economical alternative for strength recovery after crack damage has occurred," said Moore. He believes, "From an economics and simplicity standpoint, self-healing materials could become part of everyday life."

Moore co-authored a paper on this subject with graduate student and lead author Mary Caruso, former postdoctoral research associate David Delafuente, visiting University of Texas at Austin undergraduate student Victor Ho, materials science and engineering professor Nancy Sottos, and aerospace engineering professor Scott White. Funding was provided by the Air Force Office of Scientific Research and the National Science Foundation.