January 30, 2014
Nature-Inspired Carving Technique Used To Create Unbreakable Glass
redOrbit Staff & Wire Reports - Your Universe Online
Drawing inspiration from natural structures such as seashells, researchers from the McGill University Department of Mechanical Engineering have developed a new technique to create glass that will bend, but not break.“Mollusk shells are made up of about 95 percent chalk, which is very brittle in its pure form,” Professor François Barthelat explained in a statement. “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, is known to be extremely strong and tough, which is why people have been studying its structure for the past twenty years.”
While previous attempts to recreate nacre structures have been difficult, Barthelat and his colleagues took a different approach. As they explained in the Tuesday edition of the journal Nature Communications, they studied the “weak” internal boundaries or edges found in natural materials like nacre.
Afterwards, they used lasers to engrave a series of miniature, three-dimensional cracks in glass slides to create similar weak boundaries. The researchers called the results “dramatic,” noting that the engraving process made the glass deformable and strengthened its toughness of the slides by 200 times that of normal glass slides.
By carving in the networks of micro-cracks in configurations similar to the wavy edges of jigsaw puzzle pieces in borosilicate glass surfaces, Barthelat’s team was able to prevent the cracks from growing larger and spreading. Afterwards, they filled the micro-cracks with polyurethane, although the researchers said this part of the process is less essential, as the crack patterns alone are enough to prevent the glass from shattering.
While Barthelat and his co-authors opted to work with glass slides due to their accessibility, they believe the process can easily be adapted to work with any size of glass sheets – in part because people are already taking glass panels and engraving patterns and logos into them. Their research was sponsored by the Natural Sciences and Engineering Research Council of Canada (NSERC) and the Canada Foundation for Innovation (CFI).
“What we know now is that we can toughen glass, or other materials, by using patterns of micro-cracks to guide larger cracks, and in the process absorb the energy from an impact,” 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.”