Hidden energy dissipation mechanism in nacre

The defense mechanism that nacre (mother-of-pearl) uses to protect its living organism against high-speed predatory attack can provide lessons for engineered armor design. However, the underlying physics responsible for nacre's dynamic energy dissipation has hitherto remained a mystery to be uncovered. Here we demonstrate a new energy dissipation mechanism hidden in nacre and activated only upon dynamic loading, where the crack terminates its propagation along nacre's biopolymer interlayers but straightly impinges the aragonite platelets (95 vol%) in a transgranular manner. This intergranular-transgranular transition promotes the fracture energy dissipation, far exceeding that of the currently-used engineered ceramics. The mechanistic origin accounting for the enhancement of fracture energy dissipation is attributed to the unique nanoparticle architectured aragonite platelets. The dynamic manifestation in nacre can inspire a new route to design stronger-and-tougher engineered ceramic armors.