Strength - Cost
General Information
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Strength measures the resistance of a material to failure, given by the applied stress (or load
per unit area)
The chart shows yield strength in tension for all materials, except for ceramics for which
compressive strength is shown (their tensile strength being much lower)
Many applications require strong materials, e.g. screw drivers, safety belts - these lie at the
top of the chart
Unfortunately there are few cheap high strength materials (top left)
Physical Insights
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Ceramics and glasses have directional covalent bonds. They are weak in tension because
they are sensitive to small cracks or flaws.
Metals do not have directional bonds and have similar tensile and compressive properties
Cellulose microfibres make wood strong in tension along the grain
Alloys are much stronger than pure metals
Metals can be strengthened by heat treating to change the microstructure
Strength - Cost
Example Uses
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Teflon as a non stick surface for frying pans
Ceramic for fire bricks and for coatings for jet engine blades
Tungsten for light bulb filaments
Simple Questions
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Why is wood used for beams rather than stone, when stone has a higher strength?
Why is pottery weak?
Why is steel the most commonly used ‘strong’ material?
Select materials for a screwdriver.
Select materials for a glass-cutting tool.
Further Questions
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Why can polymers operate only at low temperatures when their polymer chains contain
covalent bonds like ceramics?
What is the operating temperature of a light bulb filament?
Metals and alloys
Ceramics
Polymers
Wood and wood products
Composites
Select chart:
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Young's modulus - Density
Young's Modulus - Cost
Strength - Density
Strength - Toughness
Strength - Elongation
Strength - Cost
Strength - Max service temperature
Specific stiffness - Specific strength
Electrical resistivity - Cost
Recycle Fraction - Cost
Energy content - Cost