A measure of a material’s ability to resist mechanical impact, quantified as the amount of energy required for a hammer-like pendulum to break a test specimen. The two mainstream testing configurations are Charpy and Izod.
Both tests can be performed on notched or unnotched specimens. Notched Izod is the most common method for plastics. Any given test setup covers a relatively narrow range of values. When the impact strength of a given specimen falls outside of the useful range of a test setup, "no break" may be reported instead of a numeric value.