Young's Modulus

Young's modulus measures stiffness and is a material constant, i.e. it is the same whatever the size of the test-piece.
Many applications require stiff materials, e.g. roof beams, bicycle frames - these materials lie at the top of the chart
Many applications require low cost materials, e.g. packaging foams - these materials lie to the left of the chart.
Cheap stiff materials lie towards the top left of the chart – mostly metals and ceramics.

Polymers don't seem like a good choice for stiff, cheap products - but they can be reinforced by incorporating stiffeners into the design (for instance look inside a plug).
Diamond is the stiffest material because of its full covalent bonding - but its price means it is not used for engineering applications.
Polyethylene has a wide range for Young’s modulus because the ‘bubble’ include both LDPE and HDPE.

Concrete is cheap and stiff - ideal for structures.
Cast iron is ideal for a machine-tool bed as it provides high stiffness at low cost.

What applications might require low stiffness materials?
Paper has the same Young’s modulus as oak – so why do people think it’s not as stiff?
Since wood is not that cheap, why was it used so much until recently?

Since composites don’t appear to provide stiffness at low cost - why are they used?
Why is lead used as ‘flashing’ to keep water out of buildings (e.g. roof/chimney joins).
What is different about urea formaldehyde compared to the other polymers on the chart that makes it the stiffest?
Why are ceramics, such as silicon carbide, used for machine tool tips?
Foams are stiffer than rubbers (why?), but not as strong as rubbers (why?). What are the implications for suitable applications?

Young's Modulus - Cost