Toughened glass is all around us. It's used in our car windshields, smartphone screens, and even bulletproof vests. But what happens when toughened glass breaks?

A team of researchers from the University of Cambridge and the Massachusetts Institute of Technology (MIT) has developed a new theory that helps explain how toughened glass breaks. Their findings, published in the journal Physical Review Letters, could lead to the development of stronger, more durable glass materials.

Toughened glass is made by heating and then rapidly cooling glass. This process creates a surface layer of tempered glass that is much harder and stronger than the glass beneath it. When toughened glass breaks, it typically fractures in a characteristic "spiderweb" pattern.

The new theory developed by the researchers explains why toughened glass fractures in this way. The theory shows that the spiderweb pattern is caused by a combination of factors, including the residual stresses in the glass, the shape of the cracks that form, and the way that the cracks interact with each other.

"Our theory provides a comprehensive understanding of how toughened glass breaks," said Dr. Andrea Armani, a researcher at the University of Cambridge and co-author of the study. "This understanding could be used to design tougher, more durable glass materials for a variety of applications."

The researchers plan to use their theory to study how toughened glass interacts with other materials, such as metals and ceramics. They also plan to investigate how the properties of toughened glass can be controlled by changing the manufacturing process.

"We hope that our work will lead to the development of stronger, more durable glass materials that can be used in a wider range of applications," said Armani.