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Title: Measurement of fracture toughness by nanoindentation methods: Recent advances and future challenges

In this study, we describe recent advances and developments for the measurement of fracture toughness at small scales by the use of nanoindentation-based methods including techniques based on micro-cantilever beam bending and micro-pillar splitting. A critical comparison of the techniques is made by testing a selected group of bulk and thin film materials. For pillar splitting, cohesive zone finite element simulations are used to validate a simple relationship between the critical load at failure, the pillar radius, and the fracture toughness for a range of material properties and coating/substrate combinations. The minimum pillar diameter required for nucleation and growth of a crack during indentation is also estimated. An analysis of pillar splitting for a film on a dissimilar substrate material shows that the critical load for splitting is relatively insensitive to the substrate compliance for a large range of material properties. Experimental results from a selected group of materials show good agreement between single cantilever and pillar splitting methods, while a discrepancy of ~25% is found between the pillar splitting technique and double-cantilever testing. It is concluded that both the micro-cantilever and pillar splitting techniques are valuable methods for micro-scale assessment of fracture toughness of brittle ceramics, provided the underlyingmore » assumptions can be validated. Although the pillar splitting method has some advantages because of the simplicity of sample preparation and testing, it is not applicable to most metals because their higher toughness prevents splitting, and in this case, micro-cantilever bend testing is preferred.« less
Authors:
 [1] ;  [2] ;  [3] ;  [4]
  1. Roma Tre Univ., (Italy)
  2. Technische Univ. Darmstadt, Darmstadt (Germany)
  3. Univ. of Tennessee, Knoxville, TN (United States)
  4. Univ. of Tennessee, Knoxville, TN (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
OSTI Identifier:
1242666
Grant/Contract Number:
AC05-00OR22725
Type:
Accepted Manuscript
Journal Name:
Current Opinion in Solid State and Materials Science
Additional Journal Information:
Journal Volume: 19; Journal Issue: 6; Journal ID: ISSN 1359-0286
Publisher:
Elsevier
Research Org:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 77 NANOSCIENCE AND NANOTECHNOLOGY fracture toughness; nanoindentation; cantilever; pillar; micron-scale