It Looks a Lot Like Glass, but It’s Tough as Steel

NY Times ^ | January 10, 2011 | SINDYA N. BHANOO

[GOPJ]

ping

[loungitude]

Toughness is the ability to absorb energy. Strength is stress level at which plastic deformation or fracture occurs. Plastic deformation means the material does not return to it’s original shape.

[LoneRangerMassachusetts]

Toughness is the ability to absorb energy

And the non technical way to explaine this to lay people is the example of the coat hanger. It takes a lot of work bending back and forth to break it. It's the ductile nature of steel that permits it to bend into a plastic state making it tough without easily breaking.