Research Papers: Materials and Fabrication

A New Approach for Bimaterial Interface Fracture Toughness Evaluation

[+] Author and Article Information
John Jy-An Wang, Ian G. Wright, Michael J. Lance

 Oak Ridge National Laboratory, Oak Ridge, TN 37831-6171

Ken C. Liu

 Oak Ridge National Laboratory, Oak Ridge, TN 37831-6171wangja@ornl.gov

MSC.PATRAN , Version 2005r2, MSC.Software Corporation, 2 MacArthur Place, Santa Ana, CA.

ABAQUS , Version 6.5, ABAQUS Inc., 166 Valley Street, Providence, RI.

J. Pressure Vessel Technol 130(1), 011401 (Jan 08, 2008) (9 pages) doi:10.1115/1.2826408 History: Received June 20, 2006; Revised December 05, 2006; Published January 08, 2008

A material configuration of central importance in composite materials or in protective coating technology is a thin film of one material deposited onto a substrate of a different material. Fabrication of such a structure inevitably gives rise to stress in the film due to lattice mismatch, differing coefficient of thermal expansion, chemical reactions, or other physical effects. Therefore, in general, the weakest link in this composite system often resides at the interface between the thin film and the substrate. In order to make multilayered electronic devices and structural composites with long-term reliability, the fracture behavior of the material interfaces must be known. This project offers an innovative testing procedure of using a spiral notch torsion bar method for the determination of interface fracture toughness that is applicable to thin coating materials in general. The feasibility study indicated that this approach for studying thin film interface fracture is repeatable and reliable, and the demonstrated test method closely adheres to and is consistent with classical fracture mechanics theory.

Copyright © 2008 by American Society of Mechanical Engineers
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Figure 1

Schematic diagram of the SNTT configuration

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Figure 2

Schematic diagram of the notch root geometry and the associated crack initiation sites

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Figure 3

SNTT thin film specimen design configuration

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Figure 4

Experimental setup with AE sensors attached to the specimen

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Figure 5

Residual stress profile across the U groove from Specimen 7 before the torsion test and from Specimen 3 after the torsion test

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Figure 6

(a) Specimen 7 (U groove, not precracked) and (b) Specimen 9 (U groove, precracked)

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Figure 7

Scale spallation at bottom corner of Specimen 3

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Figure 8

Defect sites at the bottom corner of the U groove from Specimen 7

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Figure 9

Torque load (top, in volts) and AE hit (bottom) time histories for Specimen 3

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Figure 10

FEM mesh near crack tip at the bottom of the U groove of the SNTT thin film sample

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Figure 11

FEM for the middle section of the SNTT thin film sample



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