European projects centre on polymers which can recover properties.
Scientists have published details of projects being carried out across Europe to create self-repairing materials.
The research centres on the creation of polymer materials with the capacity to recover properties with no or minimal external help.
Researchers from Inasmet-Tecnalia in Spain, Sheffield University and Bristol University explained that there are currently two main self-repairing technologies in polymer materials: adhesives and thermal encapsulation.
The first of these involves "stores" of adhesive found distributed in the most homogenous manner possible throughout the material.
When a crack reaches one of these nodes the adhesive is secreted together with a catalyst. The crack is then closed and the material polymerised.
There are two variants within this line of technology, depending on whether the scientists used adhesive-containing microcapsules or tubes filled with adhesive.
Inasmet-Tecnalia has worked on this line in a project undertaken for Airbus, having managed to produce a series of microcapsules and distribute them in a polymeric resin.
This was a fundamental step in finding out the difficulties that might arise in the encapsulation process.
The second method, developed by Bristol University, is a project for the European Space Agency using tubes rather than microcapsules filled with adhesive.
The thermal method uses a different repair methodology. A material, developed by the University of Sheffield, is a polymeric matrix compound, reinforced with carbon fibres.
The polymer matrix, in turn, is made of a solid solution of a thermoplastic polymer and another thermostable polymer.
In this case, when damage is detected, repair is carried out by heating the material with some device incorporated into it.
This heating is capable of raising the temperature above that of the fusion of the thermoplastic material which, as a result, melts and flows into the damaged areas so that the cracks are sealed and the component restored to its former condition.
Inasmet-Tecnalia has also worked in this field within the framework of the aforementioned project.