Lightweight composite material inspects itself: Changes in color
indicate deformations

Date:
August 23, 2021
Source:
ETH Zurich
Summary:
Researchers have developed a new type of laminate that changes
color as soon as the material is deformed. This way, the materials
researchers can kill two birds with one stone: a lightweight
composite material that inspects itself.



FULL STORY ==========================================================================
ETH Zurich researchers have developed a new type of laminate that changes colour as soon as the material is deformed. This way, the materials
researchers can kill two birds with one stone: a lightweight composite
material that inspects itself.


========================================================================== Lightweight construction has found its way into many areas, especially automotive manufacturing, shipbuilding and aircraft construction. In
addition to traditional lightweight metals such as aluminium, magnesium
or titanium, load-​bearing applications are increasingly featuring composite materials. This is driving a concurrent need to develop new techniques and methods for the early detection of damage to or even the possible failure of such as yet understudied materials.

Researchers from the Complex Materials Group at ETH Zurich, working in collaboration with researchers from the University of Fribourg, have now adopted an approach that has recently garnered attention in materials
research: they have created a lightweight material that uses a colour
change to indicate internal deformation and thus possible material
failure at an early stage.

Composed of individual layers, their laminate is translucent, break- ​resistant and yet very lightweight.

Artificial mother-​of-pearl combined with polymer The laminate
is composed of alternating layers of a plastic polymer and artificial
nacre or mother-​of-pearl. The latter is a speciality of the
Complex Materials Laboratory and is modelled on the biological example
of the mussel shell. It consists of countless glass platelets arranged in parallel, which are compacted, sintered and solidified using an polymeric resin. This makes it extremely hard and break-​resistant.

The second layer consists of a polymer to which the researchers added an indicator molecule synthesised specifically for this application at the University of Fribourg. The molecule is activated as soon as the polymer experiences stretching forces, and this changes its fluorescence. The
more the material stretches and the more of these molecules are activated,
the more intense the fluorescence becomes.

Fluorescence indicates overstressed parts "We used fluorescent molecules because you can measure the increase in fluorescence very well and
you don't have to rely on subjective perception," says Tommaso Magrini,
lead author of the study, which was recently published in the journal ACS Applied Materials and Interfaces. The system could also have been set up
to produce a colour change that would be directly perceptible from the
outside. But: "The perception of colours is subjective and it is difficult
to draw conclusions about changes in the material," Magrini says.

With the help of fluorescence, the researchers can now identify
overstressed areas within the composite material even before fractures
form. This allows early detection of vulnerable areas in a structure
before catastrophic failure occurs. One possible application of the novel laminate is in components in the load-​bearing structures found in buildings, aircraft or vehicles, where it is essential to detect their
failure at an early stage.

However, it remains to be seen whether and how the material can be
produced on an industrial scale. So far, it exists only at laboratory
scale as a proof of concept.

========================================================================== Story Source: Materials provided by ETH_Zurich. Original written by
Peter Ru"egg. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Tommaso Magrini, Derek Kiebala, Dominique Grimm, Anna Nelson,
Stephen
Schrettl, Florian Bouville, Christoph Weder, Andre'
R. Studart. Tough Bioinspired Composites That Self-Report
Damage. ACS Applied Materials & Interfaces, 2021; 13 (23): 27481
DOI: 10.1021/acsami.1c05964 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/08/210823125700.htm

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