Simultaneous improvements of strength and toughness in topologically interlocked ceramics

Mohammad Mirkhalaf, Tao Zhou, and Francois Barthelat
PNAS September 11, 2018 115 (37) 9128-9133; published ahead of print August 23, 2018 https://doi.org/10.1073/pnas.1807272115

  1. Edited by David A. Weitz, Harvard University, Cambridge, MA, and approved July 23, 2018 (received for review April 27, 2018)

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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.

Abstract

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 (50×) but also stronger (1.2×) 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.

Footnotes

  • ↵1To whom correspondence should be addressed. Email: francois.barthelat{at}mcgill.ca.

  • Author contributions: M.M. and F.B. designed research; M.M. and T.Z. performed research; M.M., T.Z., and F.B. analyzed data; M.M. and F.B. prepared the figures; and M.M. and F.B. wrote the paper.

  • The authors declare no conflict of interest.

  • This article is a PNAS Direct Submission.

  • This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1807272115/-/DCSupplemental.

Published under the PNAS license.

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Simultaneous improvements of strength and toughness in topologically interlocked ceramics
Mohammad Mirkhalaf, Tao Zhou, Francois Barthelat
Proceedings of the National Academy of Sciences Sep 2018, 115 (37) 9128-9133; DOI: 10.1073/pnas.1807272115
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