Microcracks make tougher glass

Thursday, 30 January, 2014

Imagine a glass bottle that, when dropped, doesn’t shatter but rather bends and becomes slightly deformed. Such a material could soon be possible, thanks to the humble seashell.

Professor François Barthelat and his team at McGill University in Canada have taken inspiration from the mechanics of natural structures such as seashells in order to make tougher glass.

“Mollusc shells are made up of about 95% chalk, which is very brittle in its pure form,” said Professor Barthelat. “But nacre, or mother-of-pearl, which coats the inner shells, is made up of microscopic tablets that are a bit like miniature Lego building blocks. It is known to be extremely strong and tough, which is why people have been studying its structure for the past 20 years.”

Attempts to recreate the structure of nacre proved challenging, so the team instead studied the internal ‘weak’ boundaries or edges found in natural materials like nacre, then used lasers to engrave networks of 3D microcracks in glass slides in order to create similar weak boundaries.

Using glass slides similar to those used under microscopes, the researchers were able to increase the toughness of the glass by 200 times, when compared with non-engraved slides. By engraving networks of microcracks in wavy lines - similar to the wavy edges in a jigsaw puzzle - on the surface of borosilicate glass, they were able to stop the cracks from propagating and becoming larger.

While the researchers then filled the microcracks with polyurethane, Professor Barthelat says this is not essential as the patterns of microcracks are sufficient to stop the glass from shattering. He says the process will be very easy to scale up to any size of glass sheet.

“What we know now is that we can toughen glass, or other materials, by using patterns of microcracks to guide larger cracks, and in the process absorb the energy from an impact,” Professor Barthelat said.

“We chose to work with glass because we wanted to work with the archetypal brittle material. But we plan to go on to work with ceramics and polymers in future. Observing the natural world can clearly lead to improved man-made designs.”

The research was published in the journal Nature Communications.

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