The Breaking of Brittle Materials

A long metal thread breaks more easily than a short one—an observation Leonardo da Vinci made in the 15th century. It all comes down to simple statistics: the larger an object, the more likely it is to contain a region that breaks when subject to stress. The fracture properties of brittle materials also depend on the disorder in their underlying structure: a homogeneous material like glass breaks differently than composite materials like bone and seashell. Although system size and disorder are linked in a statistical physics description of fracture, the two parameters have typically been treated separately. Now, in Physical Review Letters, Ashivni Shekhawat at Cornell University and colleagues present the first theoretical model that accounts for both at once [1]. Their model allows the authors to identify three different “phases” that characterize crack formation, and show how one phase evolves into the other as the system size or amount of disorder increases.