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Tensile Failure and Fracture of Three-Dimensional Brittle Nanolattices

Citation

Mateos Arrieta, Arturo José (2018) Tensile Failure and Fracture of Three-Dimensional Brittle Nanolattices. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/AZXG-NB17. http://resolver.caltech.edu/CaltechTHESIS:06122018-094549478

Abstract

The emergence of a new class of cellular solids, i.e., nano- and micro-architected materials, poses the question of whether they can be characterized as a continuum solid. Extensive research has shown that these ultralight and strong structural metamaterials are particularly attractive for mechanically-demanding applications; yet their susceptibility to flaws, fracture behavior, and discrete-continuum duality remains relatively unexplored. In the course of this work, we report the fabrication and tensile-to-failure response of three-dimensional ceramic nanolattices, comprised of 50nm-thick alumina tubes that are arranged into periodic 5um-wide octet-truss unit cells, with and without pre-fabricated through-thickness center notches oriented at different angles to the loading direction. In-situ uniaxial tensile experiments revealed that for all notch orientations, failure always initiated at the notch root, as would be in a monolithic material, with the tube walls at nodal junctions fracturing first, followed by instantaneous crack propagation through the discrete lattice architecture along nodal planes orthogonal to the loading direction. Measured tensile strength of 27.4 MPa was highest for the unnotched samples and decreased systematically with the increase of notch orientation to its minimum of 7.2 MPa in the orthogonally-notched samples. We found the specific tensile strength of hollow-tube octet alumina nanolattices to be 4 times higher than what has been reported for architected and bulk materials at similar low densities. Three-dimensional finite element simulations closely reproduce the observed failure mechanism and trends in failure strength. A direct comparison is made between the experimental measurements, finite element simulations, and predictions of linear elastic fracture mechanics for a self-similar monolithic tensile samples made out of an ideally-brittle solid. Results are in good agreement with the scaling of failure strengths from classical mode I fracture criteria and suggest that trajectory of crack propagation can be adequately explained by considering the connectivity of the lattice architecture. These findings imply that the continuum nature of nano-architected materials offers predictability of failure stresses, which helps enable the development of advanced materials through informed architectural design.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:nano-architected materials, fracture mechanics, nanomaterials, cellular solids, structural metamaterials, tension, failure, ceramic
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Aeronautics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Greer, Julia R.
Group:Kavli Nanoscience Institute
Thesis Committee:
  • Ravichandran, Guruswami (chair)
  • Faber, Katherine T.
  • Pellegrino, Sergio
  • Greer, Julia R.
Defense Date:30 March 2018
Non-Caltech Author Email:arturojmateos (AT) gmail.com
Record Number:CaltechTHESIS:06122018-094549478
Persistent URL:http://resolver.caltech.edu/CaltechTHESIS:06122018-094549478
DOI:10.7907/AZXG-NB17
ORCID:
AuthorORCID
Mateos Arrieta, Arturo José0000-0002-9306-3531
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:11076
Collection:CaltechTHESIS
Deposited By: Arturo Mateos
Deposited On:13 Jun 2018 23:02
Last Modified:21 Aug 2018 20:55

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