Toughness

Toughness of a plastic is measured by its resistance to impacts. It is the ability of a material to resist both fracture and deformation. One common way to discuss the toughness of a polymer is to examine the area underneath the stress - strain curve for the particular polymer. 

In general, ‘Hardness’, ‘Toughness’ and ‘Strength’ are similar terms to use, but in material science they are three distinct properties yet also share some overlap. Here are the key differences: 

· Hardness is how well material holds together when friction is applied 

· Strength is how much force is required before the material deforms. It tells us about the amount of load a material can bear 

· Toughness is the ability of a material to resist breaking when force is applied 

Toughness is the combination of strength and ductility

To be tough, a material must exhibit both fairly good strength and ductility to resist cracking and deformation under impact loading. 
Impact test signifies toughness, or impact strength, of a material that is the ability of material to absorb energy during plastic deformation. This energy absorption is directly related to the brittleness of the material. Results of impact tests are expressed in terms of either:

· Amount of energy absorbed (Nm) or 

· Amount of energy absorbed per unit cross sectional area (Nm/cm²)

Applications include:

· Measure of the energy required to crack a material

· Screen materials for impact developments

· Define uses of materials in automotive applications