Strength and toughness trade-off optimization of nacre-like ceramic composites

Bio-inspired by abalone nacre, all ceramic brick-and-mortar composites with impressive mechanical properties have been recently manufactured. Albeit comprising only brittle constituents, extrinsic reinforcement mechanisms impart to these nacre-like ceramics high toughness and non-catastrophic crack propagation properties. While several models have been developed to understand the mechanical properties of natural and synthetic brick-and-mortar materials, they have always considered a ductile interface and focused mostly on intrinsic toughening mechanisms. Modeling so far has not captured the extrinsic toughening mechanisms responsible for the properties of nacre-like ceramics. Here we show that the Discrete Element Method (DEM) can account for reinforcement mechanisms such as microcracking and crack deflection, and quantitatively assess strength, initiation toughness and crack growth toughness. Two approaches are studied to enhance strength and toughness of nacre-like ceramics, either by reinforcing the interface globally (an increase of the interface strength) or locally (addition of nano-bridges). We combine the results to provide design guidelines for synthetic brick-and-mortar composites comprising only brittle constituents.