Strengthening and toughening enhanced by mineral bridges through pinning and bridging in nacre-like materials

Many studies have revealed the significant role played by mineral bridges in the brick-and-mortar structure of nacre in enhancing the strength and toughness, which has seldom been addressed in theoretical models. Given the heterogeneities in nacre, pinning of the crack front by the platelets may readily occur when a crack propagates through them, although their bridging role in toughening has been captured frequently. To understand the strengthening and toughening mechanisms so as to achieve optimal bionic design, in this work, a Griffith crack of finite size has been considered by taking into account mineral bridges along with the effects of both pinning and bridging under plane strain deformation. The apparent strength and toughness have been examined using the model. Numerical results demonstrate that mineral bridges significantly enhance both strength and toughness, showing improved agreement with experimental results. These findings are expected to provide insights and guidance for the design of bio-inspired composites.