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Impact-resistant nacre-like transparent materials, Yin, Hannard, Barthelat, Science, 2019

 

Novelty/impact/significance:

Propose and fabricate nacre-inspired glass panels (50x50x3) that possess large-scale tablet sliding toughening mechanism, is 2-3 times more impact resistant than conventional laminated and tempered glass, and maintains transparency, high strength/stiffness.

The method (laser engraving and lamination) produces large size with high order and periodicity, and is inexpensive and scalable.

Scientific question:

How to achieve bulk impact-resistant glass while maintaining high toughness and strength/stiffness, and transparency?

 

Key of how:

Create 3D ‘brick-and mortar’ in glass to embody tablet sliding (toughness and impact resistance) and maintain transparency and hardness: laser engraves glass sheets (tablets contour aspect ratio, sheet integrity and tablet separation), select ethylene-vinyl acetate (EVA) as polymer inter-sheet layer (transparent, deformable), laminate engraved glass sheets and polymer (staggered arrangement).

Use micro-CT to quantify and verify the dominant toughening mechanism of interface shear (tablet sliding).

 

Major points (useful info):

1. To address the brittleness and low impact resistance of glass, tempering still results in catastrophic failure while lamination with polymeric interlayer does not increase impact resistance significantly.

2. The structure of nacre, staggered mineral tablets bonded by biopolymers, allow high toughness despite of ~95% mineral content through interface shearing. But manufacturing bulk nacre-structure with high toughness via large scale tablet sliding has been absent.

3. Using laser engraving to generate tablet contours (balancing integrity and separation) in glass sheets, interlayer polymer, laminating while assuring the staggered arrangements to fabricate nacre-inspired glass.

4. nacre-like glass panels are transparent (80% transmittance);

5. Comparing with glass, plain laminated (only use a small portion of the EVA interlayer toughness) in puncture, nacre-like glass show more repeatable response (governed by tablet sliding), lower strength and stiffness (due to segmented architecture, but can be improved by design), substantially increased toughness; Best design is Hex[1P4A] with L=1.5 mm.

6. Micro-CT quantifies the amount of shear deformation (tablet sliding) (sliding distance and sliding mechanism index); nacre-like panels are 2.4 times more shear deformation than plain laminated. Since the numbers agree with the energies in puncture force-displacements, the shear deformation is the main toughness source in the nacre-like glass panels.

7. In impact tests, PMMA and glass are brittle, plain laminate and tempered glass show better, but nacre-like glass has highest impact resistance, ~double that of tempered glass.

 

Work is beautiful, and writing is concise, clear, and concrete.

Here is the link of the paper: https://science.sciencemag.org/content/364/6447/1260

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