DESIGN IDEAS
❱❱ Flexible and hard all in one piece: the new plastic metamaterial MetAK, bottom; MetAK enables scoliosis corsets in modern designs with a high degree of comfort, left
“Metak is comparable to an ordinary two-
component adhesive from the hardware shop, except that more components are mixed together,” explains developer Roland Klein, from the Fraunhofer Institute for Structural Durability and System Reliability. “The production is simple, because the components do not have to be synthesised in the laboratory, but are commercially available, even though the exact formula is a secret.” The stiffness of this initially viscous
material is determined by two hardening mechanisms: irradiation with UV light and heat. The areas that should remain flexible are not irradiated, but are instead cured with heat. These areas are ideal for carrying dynamic loads, such as in the connection between a car engine and body, for example, where the joining zones in particular are exposed to high stress peaks and vibrations. “Metak has the advantage that the
rigidity is very easily adjustable,” says Klein. “You no longer need many different adhesives with different degrees of hardness, because you can flexibly adjust the material to the frequency range of the vibrations and compensate for them.” The longer and more intense the
irradiation with UV light is, the harder the material becomes. After the final heat treatment with a radiant heater or in the oven at 100-180C (depending on the application), Metak is no longer deformable, and the chemical reaction is complete. Not only can Metak be used as an
TWIN-CURED ADHESIVE CAN BE HARD AND SOFT AT THE SAME TIME
To connect components with each other, glueing is often preferred to welding or using mechanical fasteners. In particular, it is a method which contributes to taking weight out of automobiles, trains, aircraft and agricultural machines. However, the requirements placed on the
adhesive are tough: it has to be flexible enough to compensate for stress peaks in the joint zone, while still providing a rigid connection on the surface. Researchers from the Fraunhofer Institute in Munich have developed the Metak adhesive, which can be hard and soft at the same time.
8 /// Environmental Engineering /// March 2018
adhesive, but it can also be cast in a specified shape. Radiation and heat can then be used to produce hard and soft zones with flowing transitions – attractive for orthopaedic applications, for example. A Metak corset can support the deformed spine of scoliosis patients in the right places but which at the same time yields flexibly in others. This would help to avoid painful pressure points and increase wearing comfort. In addition, Metak makes it possible to produce individual corsets with a permeable structure.
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