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Fracture resistance of 3D nano-architected lattice materials

Maurizi, Marco and Edwards, Bryce W. and Gao, Chao and Greer, Julia R. and Berto, Filippo (2022) Fracture resistance of 3D nano-architected lattice materials. Extreme Mechanics Letters, 56 . Art. No. 101883. ISSN 2352-4316. doi:10.1016/j.eml.2022.101883.

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Exploiting small scale material effects and structural topology, nano-architected lattices represent a recent novel class of mechanical metamaterials, which exhibit unprecedented combination of mechanical properties. Together with scarce resistance to fracture and catastrophic failure, understanding of the fracture characteristics and properties of 3D nano-architected lattices still represents a limiting factor for the design and realization of future engineering applications. Here, using a combination of in-situ tensile fracture experiments and finite element simulations, we first show the possibility to reach stable crack growth in nano-architected materials harnessing only the intrinsic plastic toughening mechanism. Exploring the effect of lattice topology on the fracture properties, we then demonstrate similar performance between the octet and 3D kagome architecture (along one direction). Based on the experimental and numerical results, a power-scaling law of normalized crack initiation toughness with relative density ρ̅ (i.e., fraction of material per unit volume) K_(IC)/σᵧ √L ∝ ρ̅^(1.11), ρ̅^(1.17−1.27) is exhibited by the octet and 3D kagome topology, respectively, given the yield strength σᵧ and the unit cell size L. Owing to the combination of the parent material’s size effect and plasticity (3D-printed photo-resist polymer), the fracture initiation toughness (considering σᵧ) of our octet nano-architected lattices is 8 times that of previously realized macroscopic octet titanium structures. After crack initiation, the two architectures manifest rising (in average 18%) fracture resistance curves (i.e., R-curves), without catastrophic failure. In addition, we find that the fracture toughness of architected lattices, measured by means of compact tension specimens, seems not to be dependent on the sample’s thickness, forcing to re-think the plain strain toughness definition for this class of materials. Our results uncover the basic fracture characteristics of 3D architected materials exhibiting stable crack growth, providing insights for the design of light-weight, tough materials, with implications for future macro-scaled structural applications.

Item Type:Article
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URLURL TypeDescription
Maurizi, Marco0000-0002-4304-1000
Gao, Chao0000-0003-4023-0970
Greer, Julia R.0000-0002-9675-1508
Berto, Filippo0000-0001-9676-9970
Additional Information:© 2022 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license ( Received 16 May 2022, Revised 19 July 2022, Accepted 15 August 2022, Available online 19 August 2022, Version of Record 27 August 2022. JRG gratefully acknowledges the financial support of the Vannevar-Bush Faculty Fellowship from the US Department of Defense. Data availability. Data will be made available on request. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Funding AgencyGrant Number
Vannever Bush Faculty FellowshipUNSPECIFIED
Record Number:CaltechAUTHORS:20221017-767512000.2
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:117440
Deposited By: George Porter
Deposited On:17 Oct 2022 17:23
Last Modified:27 Oct 2022 16:32

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