A variety of testing methods are available to determine when a material is damaged or under stress, but what if the material itself could tell you when it was in trouble, where the problem is and its level of severity? Researchers from the Complex Materials Group at ETH Zurich recently created a self-reporting material that undergoes a fluorescent color change upon deformation, which can help engineers catch potential damage and identify areas of weakness at an early stage.
The strong, lightweight, composite material contains alternating layers of a plastic polymer and artificial nacre, also known as mother-of-pearl. The synthetic nacre, inspired and modeled after its natural counterpart found in mussel shells, consists of glass platelets arranged in parallel, which are compacted, sintered and solidified using a polymeric resin. This makes the nacre-like layers extremely hard and break-resistant.
The polymer layers contain an indicator molecule synthesized by the researcher, which is activated as soon as the polymer experiences stretching forces, changing its fluorescence. The more the material stretches, the more of these mechanophore molecules are activated, and the more intense the fluorescence becomes. Because the fluorescent signal appears before a fracture even forms, the indicator molecules can help catch defects long before a structural failure occurs. This research was published in ACS Applied Materials.
“We used fluorescent molecules because you can measure the increase in fluorescence very well and you don’t have to rely on subjective perception,” said lead author Tommaso Magrini.
This proof of concept study shows the potential of lightweight laminates that can self-report damage to help prevent failures of components such as load-bearing structures in buildings, aircrafts or vehicles. Further work may determine how the material could be produced on an industrial scale.