In addition to light metals such as aluminium, composite materials are increasingly being used in load-bearing applications. Because these new materials have not yet been tested much, methods must be developed to indicate possible failure at an early stage. Researchers at the ETH Zurich and the University of Fribourg have elegantly solved this problem with a material that is self-diagnosing, so to speak.

The researchers have created a lightweight material that uses a colour change to indicate internal deformations and thus a possible material failure before something bad happens. The laminate, composed of individual layers, is apparently transparent, break-resistant and yet very light.

Countless glass plates

The layers of the laminate consist alternately of plastic and artificial mother-of-pearl. The latter is a speciality of the ETH Laboratory for Complex Materials and is modelled on the biological example of the mussel shell. It consists of countless glass plates arranged in parallel, which are compressed, sintered (heated in a special way) and solidified by a polymer resin. This makes it extremely hard and break-resistant.

The second layer consists of a polymer to which the researchers added a synthesised indicator molecule. This molecule is activated by stretching forces that occur in the polymer. This changes its fluorescence. The stronger the stretching of the material, the more intensively it glows.