The aircraft wings or wind turbine blades themselves fill cracks that appeared after a clash or because of aging is the hope brought by numerous research projects, one of which comes from a lead product appears sufficiently effective and inexpensive.

The search for materials that can heal cracks is particularly active and has generated a lot of work. Broadly speaking, the solution makes use of epoxy resins, ie polymer, thus trained bricks chemically linked, the
monomers. In the material, reserves intact monomers are voluntarily included. When a crack occurs, it releases the monomers that are expected to go polymerize.
Ripping will be filled by the newly formed resin and will adhere to the walls of the crack.

Easier said than done… Monomers reluctant to spontaneously polymerize and we must make a solvent, energy or a catalyst to convince them.
We must therefore include in the material infrastructure complex capable of the catalyst or the solvent, or otherwise distribute energy.

Several methods have been devised, to a sophisticated technique using carbon nanotubes and a localized melting with an electric current.

In the United States, at the University of Illinois at Urbana-Champaign, the team of Scott White and Kathleen S. Toohey, presented in June material vascularized, inspired biological tissues.

Reducing the cost to launch the industrialization

In the same university, Jeffrey Moore, laboratory Murchison-Mallory, has been working with members of that team to borrow a technique already experienced: in resin, soaked a catalyst, are included microcapsules of 150 microns in diameter containing a monomer (dicyclopentadiene). When a crack propagates, it tears apart capsules, the content of which is spreading in the matrix resin where she met the catalyst, causing polymerization of
monomers. The process works perfectly, but it has a big drawback: the catalyst, based on
ruthenium, is well known (it is the catalyst for Grubbs), but much too expensive to be used on an industrial scale, albeit in a the airplane wing.

Researchers still did not give up however and successfully sought to eliminate this expensive catalyst. The capsules contain a simple solvent now,
chlorobenzene.
As for the monomers in reserve, they gathered in pockets incorporated into the resin matrix.
The crack, too, ripped the microcapsules releasing the solvent. It spreads throughout the matrix and through the pockets of monomers that leads into the hole, where they polymerize, even without the help of a catalyst.

This reaction has been observed. The team measured the restoration of 82% of the strength after healing.
Their work is not yet published but they soon will be in the journal Macromolecules.

The abandonment of the catalyst down the cost of the material. The researchers confidence in the possible industrialization process seems firm. "As a matter of vueéconomique and simplicity of manufacture, materials autoréparables could be part of everyday life," says Jeffrey Moore.
But as a first step, the researchers suggest limited applications, such as the fuselage and wings of aircraft or the blades of large wind turbines.

Note for Wind turbine

A wind turbine is a machine that converts the kinetic energy in wind into mechanical energy. If the mechanical energy is used directly by machinery, such as a pump or grinding stones, the machine is usually called a windmill. If the mechanical energy is then converted to electricity, the machine is called a wind generator, wind turbine, or wind energy converter
(WEC).
Wind turbines can be separated into two types based on the axis about which the turbine rotates. Turbines that rotate around a horizontal axis are more common. Vertical-axis turbines are less frequently used.

Note for Carbon nanotube

Carbon nanotubes (CNTs) are allotropes of carbon. A single-walled carbon nanotube (SWNT) is a one-atom thick sheet of graphite (called graphene) rolled up into a seamless cylinder with diameter on the order of a nanometer. This results in a nanostructure where the length-to-diameter ratio exceeds 1,000,000. Such cylindrical carbon molecules have novel properties that make them potentially useful in many applications in nanotechnology, electronics, optics and other fields of materials science. They exhibit extraordinary strength and unique electrical properties, and are efficient conductors of heat. Inorganic nanotubes have also been synthesized.
Nanotubes are members of the fullerene structural family, which also includes buckyballs. Whereas buckyballs are spherical in shape, a nanotube is cylindrical, with at least one end typically capped with a hemisphere of the buckyball structure. Their name is derived from their size, since the diameter of a nanotube is in the order of a few nanometers (approximately 1/50,000th of the width of a human hair), while they can be up to several millimeters in length. There are two main types of nanotubes: single-walled nanotubes (SWNTs) and multi-walled nanotubes
(MWNTs).
In figure 1, The material vascularized developed by the team of Scott White and Kathleen
S. Toohey. The microscopic tubes providing the monomers and the catalyst

In figure 2, From left to right: Jeffrey Moore (a chemist), Scott White (professor of aeronautical engineering) and Nancy Sottos (professor of engineering materials science) 

In figure 3, Resin microvascularisée fully heal