Izodtests

Izod tests refer to a family of pendulum impact tests used to determine the resistance of materials to sudden impact, with the notched Izod impact test being the most common for plastics. The test measures the energy a specimen absorbs before fracturing when struck by a swinging pendulum.

In a typical Izod test, a notched specimen is clamped in a fixed support, with the notch facing the impact. The pendulum is released from a known height and strikes the specimen, and the energy absorbed is inferred from the difference in the pendulum’s energy before and after fracture. The notch concentrates stress and governs the fracture mode, yielding a reproducible measure of impact resistance.

Specimens are usually rectangular bars with a V-shaped notch. Notched Izod impact strength is reported as energy absorbed per unit cross-sectional area, commonly in units such as kJ/m^2. Tests are often conducted at controlled temperatures because material response can be temperature dependent.

Standards and variations: Notched Izod testing is standardized in methods such as ASTM D256 and ISO 179-1. Variants exist, including unnotched Izod tests and different notch geometries. The Izod method is differentiated from the Charpy method mainly by specimen mounting and notch orientation, and the choice of method depends on material type and historical practice.

Applications and interpretation: Izod tests are widely used in quality control, material selection, and research to compare impact performance and assess the effects of processing, additives, or fillers. Limitations include sensitivity to notch quality, specimen preparation, and testing temperature; results are most meaningful when compared using the same test method and conditions.

History: The test is named after its developer in the early 20th century and has since become a standard method in plastics testing and polymer science.