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Full Record for Micrograph 587

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Micrograph no
587
Brief description
Parabolic beach marks on a polystyrene fracture surface
Keywords
beach marks Link to MATTER Glossary entry for beach marks, fracture Link to MATTER Glossary entry for fracture, polymer Link to MATTER Glossary entry for polymer, polystyrene (PS)
Categories
Fracture, Polymer
System
Polystyrene (PS)
Composition
Not specified
Standard codes
Reaction
Processing
Applications
Polystyrene is hard and inexpensive and its use is very widespread. CD cases and clear plastic cups are common examples. Domestic appliance casings are also typically made from PS
Sample preparation
The surface has been sputter-coated with gold, to give a conducting surface
Technique
Scanning electron microscopy (SEM)
Length bar
80 μm
Further information
The fracture surfaces are generally very sharp and angular, indicating fast, brittle fracture with little ductile tearing. Parabolic 'beach marks', can be seen where the fracture has grown at a speed comparable to the speed of sound in the material. This results in periodic, momentary arrests in the crack propagation and periodic ridges in the fracture surface as it advances. These indicate the direction in which the fracture has occurred. Inside the beach marks is a disc-shaped flat region where the initial fracture was progressing significantly faster than the speed of sound. There is also evidence of the fracture surface branching onto different planes as it progresses.
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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