Interfacial strength-controlled energy dissipation mechanism and optimization in impact-resistant nacreous structure

Nacre with a combination of superior strength and toughness is one of the best natural body armors due to its unique brick-and-mortar structure, which is recently regarded as the model system for the lightweight and high impact performance composite design. However, most of the studies of nacreous structure focused on static loadings or simple one-dimensional dynamic load. Our study presents 3D finite element simulation, 3D printing and drop-tower impact testing to reveal the role of interfacial strength and impact velocity in impact resistance of the nacreous structure. An optimal interfacial strength is observed at which the impact resistance reaches a maximum. Sorting of various evolving damage patterns demonstrates that the simultaneous intralayer radial cracks propagation and interlayer delamination lead to a maximal energy dissipation in the presence of the optimal interfacial strength. The phase diagram of damage patterns depending on interfacial strength and impact velocity reveals that the optimal interfacial strength decreases with increasing impact velocity. This study demonstrates that the impact-resistance of nacreous structure under different impact velocities can be enhanced by tuning the interfacial strength, and gives some guidance for advanced protective materials designs. Keywords: Nacreous structure, Impact resistance, Interfacial strength, Finite element analysis, 3D-printing, Drop-tower impact experiment