Significance: Topologically interlocked materials (TIMs) use frictional sliding to generate large deformations and build toughness in otherwise all brittle components. TIMs can be up to 10 times more impact resistant than their monolithic form, but this improvement usually comes at the expense of static strength. Here we report a TIM design based on octahedral blocks which is not only much tougher (50×) than monolithic plates of the same material, but also stronger (1.2×). With no evidence of upper bounds for strength and toughness, TIMs have a tremendous potential as high-performance structural materials. Based on our experiments we propose a nondimensional “interlocking parameter” which could guide the exploration of new TIM designs and other new architectured systems.

Crocodiles, armadillo, turtles, fish and many other animal species have evolved flexible armored skins in the form of hard scales or osteoderms, which can be described as hard plates of finite size embedded in softer tissues. The individual hard segments provide protection from predators, while the relative motion of these segments provides the flexibility required for efficient locomotion. In this work, we duplicated these broad concepts in a bio-inspired segmented armor. Hexagonal segments of well-defined size and shape were carved within a thin glass plate using laser engraving. The engraved plate was then placed on a soft substrate which simulated soft tissues, and then punctured with a sharp needle mounted on a miniature loading stage. The resistance of our segmented armor was significantly higher when smaller hexagons were used, and our bio-inspired segmented glass displayed an increase in puncture resistance of up to 70% compared to a continuous plate of glass of the same thickness. Detailed structural analyses aided by finite elements revealed that this extraordinary improvement is due to the reduced span of individual segments, which decreases flexural stresses and delays fracture. This effect can however only be achieved if the plates are at least 1000 stiffer than the underlying substrate, which is the case for natural armor systems. Our bio-inspired system also displayed many of the attributes of natural armors: flexible, robust with 'multi-hit' capabilities. This new segmented glass therefore suggests interesting bio-inspired strategies and mechanisms which could be systematically exploited in high-performance flexible armors. This study also provides new insights and a better understanding of the mechanics of natural armors such as scales and osteoderms.