General Information
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.
Physical Insights
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.
Example Uses
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.