Materials combining optical transparency and mechanical strength are highly demanded for electronic displays, structural windows and in the arts, but the oxide-based glasses currently used in most of these applications suffer from brittle fracture and low crack tolerance. We report a simple approach to fabricate bulk transparent materials with a nacre-like architecture that can effectively arrest the propagation of cracks during fracture. Mechanical characterization shows that our glass-based composites exceed up to a factor of 3 the fracture toughness of common glasses, while keeping flexural strengths comparable to transparent polymers, silica- and soda-lime glasses. Due to the presence of stiff reinforcing platelets, the hardness of the obtained composites is an order of magnitude higher than that of transparent polymers. By implementing biological design principles into glass-based materials at the microscale, our approach opens a promising new avenue for the manufacturing of structural materials combining antagonistic functional properties.
Bulk materials with remarkable mechanical properties have been developed by incorporating design principles of biological nacre into synthetic composites. However, this potential has not yet been fully leveraged for the fabrication of tough and strong materials that are also optically transparent. In this work, a manufacturing route that enables the formation of nacre‐like mineral bridges in a bioinspired composite consisting of glass platelets infiltrated with an index‐matching polymer matrix is developed. By varying the pressure applied during compaction of the glass platelets, composites with tunable levels of mineral bridges and platelet interconnectivity can be easily fabricated. The effect of platelet interconnectivity on the mechanical strength and fracture behavior of the bioinspired composites is investigated by performing state‐of‐the‐art fracture experiments combined with in situ electron microscopy. The results show that the formation of interconnections between platelets leads to bulk transparent materials with an unprecedented combination of strength and fracture toughness. This unusual set of properties can potentially fulfill currently unmet demands in electronic displays and related technologies.
The
increasing use of lightweight composite materials in structural
applications requires the development of new damage monitoring technologies
to ensure their safe use and prevent accidents. Although several molecular
strategies have been proposed to report damage in polymers through
mechanochromic responses, these approaches have not yet been translated
into lightweight bioinspired composites for load-bearing applications.
Here, we report on the development of bioinspired laminates of alternating
polymer and nacre-like layers that combine optical translucency, high
fracture toughness, and damage-reporting capabilities. The composites
signal damage via a fluorescence color change that arises from the
force activation of mechanophore molecules embedded in the material’s
polymer phase. A quantitative correlation between the applied strain
and the fluorescence intensity was successfully established. We demonstrate
that optical imaging of mechanically loaded composites allows for
the localized detection of damage prior to fracture. This fluorescence-based
self-reporting mechanism offers a promising approach for the early
detection of damage in lightweight structural composites and can serve
as a useful tool for the analysis of fracture processes in bulk transparent
materials.
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