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Delamination of stiff islands on stretchable substrates. Zhigang Suo Harvard University. Lu, Yoon, Suo Int. J. Mater. Res. 98, 717 (2007). The future of knowledge?. Information. Display. Hermetic coating. Polymer substrate. Mechanical Challenges. Island crack. Coating crack. - PowerPoint PPT Presentation
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1
Delamination of stiff islands on stretchable substrates
Zhigang Suo
Harvard University
Lu, Yoon, SuoInt. J. Mater. Res. 98, 717 (2007)
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The future of knowledge?
Information Display
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Flexible electronics
MechanicalMechanicalChallengesChallenges
Island Island debonddebond
Metal Metal fatiguefatigue
CoatingCoatingcrackcrack
Island Island crackcrack
Polymer substrate
Hermetic coating
4
Island debond
6105200
1 GPa
MPa
E
E
DLC
PDMS 6105200
1 GPa
MPa
E
E
DLC
PDMS
025.0200
5
GPa
GPa
E
E
xSiN
Kapton
Lacour, Wagner, Narayan, Li, Suo, 2006Bhattacharya, Salomon & Wagner, 2006
Debond at 5.6% strain
5101100
1 GPa
MPa
E
E
DLC
PDMS
No debond at 25% strain
islands square SiN 4040 2xμm islands square DLC 200200 2μm
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Energy release rate depends on flaw size
G
maxG
maxG
Design criterion
aa
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Initiation
2211
21, ijijij r
k
r
kr 21~ aG
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Steady state
G
a
Gss
Suo and Hutchinson, IJF (1990)
hEg
G applfss2
2
applappl
h
8
Converging debond
Ligament length 2c
1
2 11
8
fsapp EE
cG He, Evans & Hutchinson, 1996
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Effect of substrate compliance on G(a)
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Gmax overshoots Gss
Overshooting
Gss
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Critical island size
i
With the same interface toughness and the same applied strain, more compliant substrate allows larger critical island size
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Summary
• Islands debond when exceeding critical size.
• Gmax overshoots Gss.
• Critical island size is large when the substrate is compliant.
Lu, Yoon, Suo, Int. J. Mater. Res. 98, 717 (2007)