Nacre's brick–mortar structure suppresses the adverse effect of microstructural randomness

Biological materials have evolved various degrees of robustness against microscopic defects and structural randomness. Of particular interest here is whether and how nacre's brick–mortar structure suppresses the adverse effect of microstructural randomness. To this end, a tension–shear–chain (TSC) network model, combined with the virtual internal bond concept, is adopted to investigate the effects of microstructural randomness of nacre, where we show that the ensemble strength and failure behaviors of a larger TSC model exhibit substantially lower randomness. Our results indicate that the staggered brick–mortar structure renders nacre insensitive to microstructural randomness, resulting in enhanced resistance to strain localization and crack initiation at weaker interfaces. The influence of microstructural randomness on the size effect of the ensemble mechanical properties of nacre is also revealed. This study provides further insights and guidelines for designing strong and robust nacre-mimic composites.