Impact resistant nacre like transparent materials
Nacre inspired toughened glass Nacre is a biological composite that is present in seashells. This composite contains a small amount of organic material that toughens brittle ceramics, such that a highly regular three dimensional brick and mortar assembly of microscopic mineral tablets is bonded together with biopolymers. Synthetic nacres have not been able to capture the large scale sliding of the bricks that is key to enhancing toughness. Yin et al. applied this model to toughening glass, where square or hexagonal borosilicate glass sheets were bonded together using ethylene vinyl acetate interlayers (see the Perspective by Datsiou) This generated a structure that allows glass plates to slide past each other. The resulting five layered glass composite was deformable and impact resistant, while maintaining high stiffness, flexural strength, surface hardness, and transparency. Science, this issue p. 1260; see also p. 1232 A ductile, yet hard, nacre inspired glass outperforms laminated glass and tempered glass in impact resistance. Glass has outstanding optical properties, hardness, and durability, but its applications are limited by its inherent brittleness and poor impact resistance. Lamination and tempering can improve impact response but do not suppress brittleness. We propose a bioinspired laminated glass that duplicates the three dimensional "brick and mortar" arrangement of nacre from mollusk shells, with periodic three dimensional architectures and interlayers made of a transparent thermoplastic elastomer. This material reproduces the "tablet sliding mechanism," which is key to the toughness of natural nacre but has been largely absent in synthetic nacres. Tablet sliding generates nonlinear deformations over large volumes and significantly improves toughness. This nacre like glass is also two to three times more impact resistant than laminated glass and tempered glass while maintaining high strength and stiffness.
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