Toughness can be defined as the resistance of a specimen to impact applied onto it, as well as resistance to fracture and deformation. For polymers, one can examine the area using a stress-strain curve that was designated for the sample being tested.

In material science, a materials hardness, toughness, and strength are all three unique characteristics that have similarities to them. They are differentiated by the terms below:

• Hardness – The durability of a material once introduced to a force of friction
• Strength – A measure of the force required to deform a material, and how much force it can be loaded with.
• Toughness – The ability of a material to not break upon the application of force and is also the combination of strength of a material, as well as its ductility.

For a material to have toughness, it must be characterized by a good measure of strength, ductility, and resistance to cracks and deformities when impacted by specific loads.

The Impact test measures the toughness, also called the impact strength, of a specific material. It measures the absorption of energy during deformation, of which the results are directly related to the materials brittleness. The results of the Impact test are expressed in either:

• The measure of absorbed energy (Nm/) or;
• The measure of absorbed energy per unit cross-sectional area (Nm/cm2)