Hindered crack propagation in materials with periodically varying Young's modulus - Lessons from biological materials

Many biological materials, such as glass sponges, nacre or bone have a lamellar structure. While it is well known that weak interfaces between lamellae may deflect cracks and, thus, increase the toughness, we analyze the influence of periodic variations in Young's modulus. Even without weak interfaces, a ratio of 5 between maximum and minimum modulus can be sufficient to stop a crack in the vicinity of the stiffness minimum.