Flaw-driven Failure in Nanostructures
Abstract
Understanding failure in nanomaterials is critical for the design of reliable structural materials and small-scale devices that have components or microstructural elements at the nanometer length scale. No consensus exists on the effect of flaws on fracture in bulk nanostructured materials or in nanostructures. Proposed theories include nanoscale flaw tolerance and maintaining macroscopic fracture relationships at the nanoscale with virtually no experimental support. We explore fracture mechanisms in nanomaterials via nanomechanical experiments on nanostructures with pre-fabricated surface flaws in combination with molecular dynamics simulations. Nanocrystalline Pt cylinders with diameters of ~120 nm with intentionally introduced surface notches were created using a template-assisted electroplating method and tested in uniaxial tension in in-situ SEM. Experiments demonstrate that 8 out of 12 samples failed at the notches and that tensile failure strengths were ~1.8 GPa regardless of whether failure occurred at or away from the flaw. These findings suggest that failure location was sensitive to the presence of flaws, while strength was flaw-insensitive. Molecular dynamics simulations support these observations and show that incipient plastic deformation commences via nucleation and motion of dislocations in concert with grain boundary sliding. We postulate that such local plasticity reduces stress concentration ahead of the flaw to levels comparable with the strengths of intrinsic microstructural features like grain boundary triple junctions, a phenomenon unique to nano-scale solids that contain an internal microstructural energy landscape. This mechanism causes failure to occur at the weakest link, be it an internal inhomogeneity or a surface feature with a high local stress.
Additional Information
X.W.G. is grateful for financial support from the National Defense Science and Engineering Graduate (NDSEG) Fellowship, 32 CFR 168a. JRG acknowledges the financial support of the National Science Foundation (DMR-1204864). X.W.G. and J.R.G. thank the Kavli Nanoscience Institute at Caltech for the availability of critical cleanroom facilities. We thank V. Deshpande and D. Jang for helpful discussion, and D. Jang and C. Garland for TEM assistance. The authors gratefully acknowledge the financial support from the Agency for Science, Technology and Research (A*STAR), Singapore and the use of computing resources at the A*STAR Computational Resource Centre, Singapore.Attached Files
Submitted - 1307.3182.pdf
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Additional details
- Eprint ID
- 39614
- Resolver ID
- CaltechAUTHORS:20130729-080552163
- National Defense Science and Engineering Graduate (NDSEG) Fellowship
- 32 CFR 168a
- NSF
- DMR-1204864
- Agency for Science, Technology and Research (A*STAR)
- Created
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2013-07-29Created from EPrint's datestamp field
- Updated
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2023-06-02Created from EPrint's last_modified field
- Caltech groups
- Kavli Nanoscience Institute