---
term: "Izod Impact Test"
category: "impact-testing"
shortDefinition: "A notched cantilever specimen is struck on its notched face by a pendulum; absorbed energy reflects toughness with a different stress distribution than Charpy."
formula: "KU = E0 − E1"
relatedStandards: ["ASTM E23","ISO 148-1"]
url: "https://vectorbtc.com.tr/resources/glossary/izod-impact-test/"
---

The **Izod impact test** clamps one end of a **notched bar** as a **cantilever** and strikes the face containing the notch with the pendulum tip. The notch experiences higher bending constraint near the clamp compared to the three-point Charpy arrangement, altering triaxiality and shifting absorbed energy for the same material and temperature.

Izod historically dominated **plastics** specifications (ASTM D256) and some metal curricula; structural steel qualification more often standardizes **Charpy**. When legacy drawings reference both, **do not mix databases** without correlation work.

Specimen preparation demands a **sharp, square notch** within tolerance; plastic deformation during notching absorbs energy and lowers reported toughness. Striker alignment and anvil gap must be verified per equipment manuals.

For polymers, Izod distinguishes **notched vs unnotched** reporting; notched Izod relates to **practical stress concentrations** in molded features.