Self-healing airplanes are on the horizon

December 27, 2007

Self-healing airplanes are on the horizon

By AOPA ePublishing staff

Scientists have developed technology where airplanes can heal their own skins and engine parts can protect themselves from hazardous materials. Enter the low-maintenance airplane.

University of Illinois researchers are working on a process where the damage itself triggers the repair mechanism in epoxy-based materials. Imagine a composite fuselage that always looks pristine.

When a crack forms in the epoxy material using this approach, microcapsules containing chlorobenzene shear. The solvent disperses into the matrix, where it finds pockets of unreacted epoxy monomers. The solvent then carries the latent epoxy monomers into the crack, where polymerization takes place. This restores structural integrity.

In fracture tests, self-healing composites recovered their original strength by 82 percent. The researches had experimented with a previous process that utilized a catalyst embedded in the epoxy matrix, but it proved too expensive for commercial applications.

"Our new self-healing system is simple, very economical, and potentially robust," said professor Jeffrey Moore. "From an economics and simplicity standpoint, self-healing materials could become part of everyday life."

Repelling oil

Engineers at MIT, meanwhile, have developed a simple process for manufacturing materials that strongly repel oils. This is important for protecting parts that get soaked in fuel such as rubber gaskets and O-rings.

Oils and other hydrocarbons spread out over surfaces due to their low surface tension. Water, on the other hand, has high surface tension and forms droplets. Surface tension is a measure of the attraction between molecules of the same substance. The difference in surface tension explains why water rolls off a duck's feathers, but oil-coated feathers have to be washed in soap.

"Nature has developed a lot of methods for waterproofing, but not so much for oil-proofing," said professor Gareth McKinley.

The MIT team overcame the surface-tension problem by designing a material composed of specially prepared microfibers that cushion droplets of liquid. The droplets sit just above the material's surface. The microfibers can be applied to many types of surfaces such as metal, glass, and plastic. They can even be applied to biological surfaces like plant leaves, using a process known as electrospinning.

December 27, 2007