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Full Record for Micrograph 570

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Micrograph no
570
Brief description
Strain-induced birefringence in a notched polycarbonate bar
Keywords
bending, birefringence Link to MATTER Glossary entry for birefringence, polycarbonate (PC), polymer Link to MATTER Glossary entry for polymer, stress Link to MATTER Glossary entry for stress
Categories
Polymer
System
Polycarbonate (PC)
Composition
Not specified
Standard codes
Reaction
Processing
Applications
Polycarbonate is a clear and relatively tough plastic used to make shatterproof windows, lenses and even helmets. It is also used to make compact discs.
Sample preparation
A notch has been cut in the bar to illustrate stress concentration. A four-point bending rig is used to apply stress.
Technique
Cross-polarised light microscopy
Length bar
6 mm
Further information
The colours in the image are the result of birefringence and relate to the strain-induced alignment of the polycarbonate molecules. Because the specimen is below the glass transition temperature of PC (145 deg C), the material will relax when the stress is removed and there will be no residual alignment. The colours reveal the pattern of stress concentration around the notch.
Contributor
J A Curran
Organisation
Department of Materials Science and Metallurgy, University of Cambridge
Date
03/10/02
Licence for re-use
Attribution-Non-Commercial-Share Alike 2.0 UK: England & Wales
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