research presentation of brandtner-hafner fracture analytics at in-adhesives symposium 2017
TRANSCRIPT
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INTERFACE FRACTURE BEHAVIOUR
OF INDUSTRIAL ADHESIVES:
A NOVEL EVALUATION APPROACH
FOR ADHESIVE SELECTION
by
Symposium on Innovations in
Adhesives and their Applications
Munich, Germany,
February 14-15, 2017
Dr. Martin BRANDTNER-HAFNER
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Introduction• Look at the schematical structure of a bonding
• You will find different sections with various properties
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Source: Habenicht (2005)
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Introduction• Look at the schematical structure of a bonding
• You will find different sections with various properties
• There, the interface is the „weak spot“
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Source: Habenicht (2005)
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Introduction• If a crack appears, it is essential how it turns out.
• Six different „Failure Modes“ may occur:
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Source: ASTM D5575 (2006)
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Source: Habenicht (2005)
Mechanical Testing of Adhesive Composites
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Mechanical Testing of Adhesive Composites
Source: Habenicht (2005)
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Limitations of Mechanical Testing
• Testing of BONDING ≠ Testing of CRACKING
• Based upon Continuummechanics, NOT Fracture Mechanics
• Just ONE PARAMETER is used to rate
the safety of the WHOLE STRUCTURE (i.e. „Strength“)
• No Statements about Cracking Behaviour possible
• Standardised testing often limits „Thinking Beyond“.
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Fracture Mechanical Considerations
Crack Opening Modes
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Source: Brandtner-Hafner (2016)
Type Loading Condition Cracking Condition
Mode I Tensile, Bending Crack opening
Mode II Biaxial – Tensile/ Pressure In-Plane Shearing
Mode III Torsion Cross-Plane Shearing (Tearing)
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Fracture Mechanical Considerations
Source: Brandtner-Hafner (2016)
Fracture Prozess Zones
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Fracture Mechanical Considerations
Source: Brandtner-Hafner (2016)
Fracture Prozess Zones
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Fracture Mechanical Considerations
Source: Brandtner-Hafner (2016)
Fracture Prozess Zones
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Fracture process gets more complex when
there are different bonding partners.
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Fracture Mechanical Considerations
Fracture Stability Conditions
Source: Brandtner-Hafner (2016)
Type Fracture Condition
A unstable
B semi-stable
C stable
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Fracture Mechanical Considerations
Fracture Stability Conditions
Source: Brandtner-Hafner (2016)
Type Fracture Condition
A unstable
B semi-stable
C stable
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„running crack“
„controlled crack“
total failure
limited failure
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Fracture Mechanical Considerations
Fracture Stability Conditions
Source: Brandtner-Hafner (2016)
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Type Fracture Condition
A unstable
B semi-stable
C stable
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Experimental Investigations
Adhesive Candidates for Fracture Mechanical Testing:
Name Chemical Basis
A Acrylate 1K
B MS-Polymer 1K
C Polyurethane 2K
D Acrylonitrile 1K
E Polyurethane 1K
F Polyurethane 1K
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Results
Source: Brandtner-Hafner (2016)
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Results
Source: Brandtner-Hafner (2016)
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Opposing Correlation between
„STRENGTH“ & „RESISTANCE“
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Results
Source: Brandtner-Hafner (2016)
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Results
Source: Brandtner-Hafner (2016)
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Results
Source: Brandtner-Hafner (2016)
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Colour = „Fracture CONDITION“
Size = „Fracture RESISTANCE“
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Results
Source: Brandtner-Hafner (2016)
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Colour = „Fracture CONDITION“
Size = „Fracture RESISTANCE“
E & F are the right choice!
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Concluding Remarks
1. Use adhesives showing maximum fracture resistance:
i.e. PU-1K for bonding wood.
2. Avoid adhesive systems tending to crack unstable:
i.e. they are too brittle → low fracture toughness.
3. Do not rely on just one engineering parameter alone
when considering adhesives for your application.
i.e. tensile strength, peel strength, elastic modulus,...
4. Do not rely just on engineering standards alone
when choosing the best-fitting adhesive system.
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Thank you!Dr. Martin Brandtner-Hafner
Fracture Mechanics Professional
E-Mail: [email protected] · Web: www.brandtnerhafner.com