Simultaneous improvements of strength and toughness in topologically interlocked ceramics

Topologically interlocked materials (TIMs) are an emerging class of architectured materials based on stiff building blocks of well controlled geometries which can slide, rotate, or interlock collectively providing a wealth of tunable mechanisms, precise structural properties, and functionalities. TIMs are typically 10 times more impact resistant than their monolithic form, but this improvement usually comes at the expense of strength. Here we used 3D printing and replica casting to explore 15 designs of architectured ceramic panels based on platonic shapes and their truncated versions. We tested the panels in quasi-static and impact conditions with stereoimaging, image correlation, and 3D reconstruction to monitor the displacements and rotations of individual blocks. We report a design based on octahedral blocks which is not only tougher (50x) but also stronger (1.2x) than monolithic plates of the same material. This result suggests that there is no upper bound for strength and toughness in TIMs, unveiling their tremendous potential as structural and multifunctional materials. Based on our experiments, we propose a nondimensional interlocking parameter which could guide the exploration of future architectured systems.