Izod impact test

A pendulum impact test in which a notched or unnotched bar specimen, supported at both ends, is struck by a swinging hammer and the energy absorbed in fracture is measured. It is used to compare the toughness of plastics, composites and metals; the plastics version is standardised in ISO 179.

The ability of a material to absorb energy and deform without fracturing, combining strength with ductility. Tough materials resist impact and flaw growth, whereas strong but brittle materials can fail suddenly.