Strength and stability in architectured spine-like segmented structures

Architectured and segmented material designs have recently emerged as a powerful approach to increasing the strength and toughness of brittle materials. Architectured materials are made of regular building blocks that can collectively slide, rotate, separate or interlock, providing a wealth of tunable mechanisms and properties. In this work we have used experiments and modeling to explore the mechanical response of idealized segmented systems made of a linear array of cubes subjected to axial pre-compression and to a transverse force. From simple tabletop experiments with playing dice with instrumented tests on 3D printed cubes and simple models, we highlight the effects of axial pre-compression, number of blocks, friction coefficient and surface morphology on strength, energy absorption (toughness) and stability (catastrophic vs. graceful failure). We identified two failure modes in this segmented system: a sliding mode where one or more blocks slide on one another, and a “hinging” mode where some interfaces open and rotate about hinge points. The failure mode transition between hinging and sliding was established, to assist the design of modern architectured structures and materials. Finally, we demonstrate that enriching the morphology of the cubes with curved interfaces (akin to the vertebrae in the spine of reptiles) delays hinging and improves stability.