Modeling of a biological material nacre: Waviness toughness model

ABSTRACT Hard biological materials such as nacre, bone, and teeth exhibit high values of toughness although it is meanly made of a ceramic material. Ceramic materials are brittle and fail in a catastrophic manner therefore they have low values of toughness. Researchers have been curious in examining the reasons behind such performance. It has been found that the staggered structure of these materials, that is brittle tablets embedded into a soft matrix, is the main reason that allows for multiple toughening mechanisms to operate at different length scales. In addition, it has been shown that the tablets are not flat. There is some waviness that generates hardening and spreading of nonlinear deformation leading to high values of toughness. The effect of waviness was not included in previous analytical toughness models. In the present work, a toughness model based on J-integral approach is developed that considers the waviness. Crack resistance curve, denoted by R-curve, is obtained that agrees with the experimental results. The developed toughness model aids in the design and optimization of nacre-like materials.