Numerical investigation on the enhanced damping behavior of bio-inspired nacreous composites by introducing interlocked structure.

Due to the unique "Brick-and-Mortar" structure, nacre exhibits extraordinary mechanical properties such as high strength and toughness, which are naturally exclusive in traditional engineering materials. The main threat to the shell is the impact load along the direction perpendicular to the lamellar structure. However, how it attenuates stress wave and dissipates kinetic energy during impact events remains unclear, especially along different loading directions (the directions perpendicular and parallel to the lamellar structure). In this paper, damping performance of nacreous bio-inspired composites is investigated to evaluate the energy dissipation from the perspective of dynamic modulus using theoretical and numerical methods. It is found that the stress states and Poisson's ratio of the "mortar" exert remarkable influence on composites' loss modulus. Moreover, the predicted optimal aspect ratio in this work is consistent with the previously reported experimental observation. Additionally, by introducing interlocked structure, the composites show strong direction-dependent damping behaviors, and the enhanced loss modulus is observed both in longitudinal and normal direction. The findings are not only expected to achieve a deep understanding of the dynamic energy dissipation mechanism of nacre, but also to provide a guideline for design of bio-inspired composites responding to shock loads.