Scope:

Unnotched Izod Impact ASTM D4812 is a single-point test, and it evaluates the resistance of a material to impact from a swinging pendulum. Izod impact is the kinetic energy required to initiate fracture and continue until the test specimen is broken. This test provides a quick and easy quality control check to compare materials for general toughness and determine if a material meets specific impact properties.

Test Procedure:

A pendulum impact test fixture is used for this test. First, the specimen bar is clamped into the fixture keeping the thin edge facing towards the striking edge of the pendulum. Then, the striking pendulum is released to strike through the specimen. A heavier hammer is used to achieve failure if a breakage does not occur.

Specimen size:

For the ASTM D4812 test, the standard specimen measurement is 64 mm × 12.7 mm × 3.2 mm (2½ × ½ × 1/8 inch). The thickness of the specimen is usually 3.2 mm (0.125 inches); however, the ideal thickness is 6.4 mm or 0.25 inches so that the specimen does not bend or crush easily. Type 1A multipurpose specimen, of dimensions 80 mm × 10 mm × 4 mm, with the end tabs cut off, is used as the standard specimen for ISO 180.

Data:

Izod impact energy is expressed in J/m or ft-lb/in. To calculate Impact strength, impact energy (in J or ft-lb) is divided by the thickness of the specimen. The test result is expressed as the average of 5 specimens.

ISO impact strength is stated in kJ/m². Dividing impact energy (J) by the area under the notch gives the impact strength. The test result contains an average of data obtained for ten specimens.

A higher value of the resulting number indicates a tougher material.