Charpy / Izod Impact Tester

Izod/Charpy Impact Tester FAQs

What is impact testing of materials?

Impact testing is a critical evaluation method for measuring the toughness of a material. It enables engineers, manufacturers, and researchers to understand how different materials react when they experience a sudden high force or shock .

Why is impact testing important?

Impact testing is vital for helping industries determine the reliability and safety of a product in real-world conditions when it’s subjected to sudden impact and stress. By selecting the appropriate materials for each component and its subsequent application, manufacturers can be confident they’re robust enough to ensure optimum functionality, performance, and most importantly safety. For example, automotive engineers need to assess the crashability of vehicle components like bumpers and front panels, as they’re the initial components to absorb force during collisions.

It’s also important for compliance with stringent safety and impact testing quality standards like ASTM E23 and ISO 180. This brings accuracy, consistency, and integrity to your impact test results, giving complete faith in the durability of the materials to withstand high-force or shock loads, and prevent catastrophic failures.

Charpy impact test vs Izod impact test

Two of the most common methods for measuring how much energy a material can absorb before it breaks are the Charpy impact test and the Izod impact test. Both work on the same principle, where the specimen is held firmly and a weighted pendulum strikes it. The amount of energy absorbed by the breaking specimen is then measured.

Despite their similarities in using pendulum-based methods to assess impact resistance, their differences in energy levels, notch orientation, and specimen position make each test suited for different conditions, materials, and industry standards.

What is a Charpy impact test?

Charpy impact tests are excellent for testing ductile materials such as metals. In industries like aerospace and automotive where materials must withstand sudden, high-energy impacts, the Charpy method is usually the better option (over Izod impact testing).

It’s often performed at low temperatures to evaluate how a material transitions from ductile to brittle failures, with U-notch and V-notch testing options providing greater versatility for testing a wider range of materials under different conditions.

How does the Charpy impact test work?

1. The sample is placed horizontally with the notch facing away from the pendulum.
2. A pendulum hammer swings down and strikes the middle of the specimen, directly opposite the notch, delivering a more concentrated, smaller energy load compared to the Izod test.
3. The energy absorbed by the specimen during fracture is measured based on the decrease in the pendulum’s swing height after impact.

Charpy impact test diagram showing a horizontally supported specimen with a central notch, struck by a pendulum hammer at the midpoint, supported at both ends.

When is a Charpy impact test required?

• In applications that handle metals, especially where durability and toughness are critical (some plastics and polymers can also be tested using this method).
• When assessing the ductile-to-brittle transition temperature — this is crucial for materials used in cold environments.
• When evaluating material consistency and weld quality in critical structures.

Charpy impact test standards

ISO standards (Charpy)

ASTM standards (Charpy)

What is a Izod impact test?

Also used to measure a material’s toughness, the Izod test uses only a V-notch, and is typically used for polymers, composites and metallic materials. It’s used by manufacturers in industries like aerospace, engineering consumer goods and packaging, to see how their products respond to accidental drops and collisions.

The key differences in the test itself to note (see below) are the notched specimen is positioned vertically instead of horizontally, and the pendulum hammer strikes the free end (rather than the midpoint) to measure how well the material can resist a single-energy impact.

How does the Izod impact test work?

1. The specimen is positioned vertically, clamped at one end, with the notch facing the hammer. It should resemble a cantilever beam.
2. The pendulum hammer swings down and strikes the specimen at a single point directly above the notch.
3. The energy needed to fracture the material is calculated from the pendulum hammer’s remaining motion following impact.

Izod impact test diagram showing a vertically clamped specimen with a notch, struck by a pendulum hammer at the impact point, with the sample fixed at one end.

When is a Izod impact strength test required?

• For industries working with lightweight materials like plastics and resins that need to be resistant to notch sensitivity.
• When you need insight into how brittle materials behave under sudden force in real-world conditions.
• As the sample is positioned vertically, Izod testing is most effective for materials that are loaded from height, such as beams or shafts.

Izod impact test standards

ISO standards (Izod)

NB: There is no standalone ISO Izod standard for metals – metallic Izod testing under ISO is covered via ASTM E23 or national standards.

ASTM standards (Izod)

How AML can make a positive impact on your Charpy and Izod tests

As leaders in the field of scientific instrumentation, you can depend on AML Instruments to supply you with a state-of-the-art Charpy and Izod test instrument that offers unique insights into the toughness and fracture behaviour of your materials.

However, it’s crucial you understand the similarities and differences between these two popular impact testing methods, so you can evaluate material toughness with certainty and ensure compliance with ISO and ASTM standards.

If you’re unsure which method to use, please contact us for a free consultation.