What Is Izod Impact?
In the Izod test, the specimen is clamped vertically at one end, and the free end is struck by a pendulum hammer on the notch side. The energy expended in fracture is measured and divided by the cross-sectional area under the notch to calculate impact strength.
Purpose of Izod Impact
The purpose is to assess notch sensitivity and brittleness under sudden loading, particularly in plastics. The difference between notched and unnotched results for the same material shows its sensitivity to stress concentration.
Which Products Is Izod Impact Applied To?
- Thermoplastic injection-moulded parts
- Reinforced and filled plastics
- Electrical insulating materials
- Appliance and automotive interior trim plastics
- Metallic specimens (with the ASTM E23 Izod setup)
In Which Sectors Is Izod Impact Used?
Standards Related to Izod Impact
- ISO 180 (plastics — determination of Izod impact strength)
- ASTM D256 (determining the Izod pendulum impact resistance of plastics)
- ISO 179-1 (Charpy equivalent; referenced for comparison)
- ASTM E23 (Izod setup for metallic materials)
Izod Impact Conditions
- Specimen mounting
- Clamped at one end; notch aligned with the vice
- Notch
- Machined to the radius and depth defined in the standard
- Hammer energy
- Selected to suit the specimen's fracture energy
- Conditioning
- In the standard atmosphere; separate conditioning for temperature-dependent studies
Equipment for Izod Impact
- Izod pendulum impact machine with interchangeable hammers
- Notching machine and notch-checking setup
- Conditioning chamber
- Specimen measurement equipment
Sample Requirements for Izod Impact
- Specimens must be to standard dimensions and preferably taken from the same mould.
- The notch must be machine-cut; cutter tip wear must be monitored.
- For injection-moulded parts, flow direction affects the result and must be reported.
- The number of specimens defined in the standard is tested.
- The conditioning period must be completed before testing.
Duration of Izod Impact
The break itself takes seconds. Total duration is set by notching and conditioning; for plastics, conditioning usually exceeds a day.
Izod Impact Procedure
- 1Specimens are measured and notched.
- 2Notch geometry is checked.
- 3Specimens are conditioned in the standard atmosphere.
- 4The specimen is clamped in the vice with the notch facing the impact direction.
- 5A hammer of suitable energy is selected and the pendulum is released.
- 6Absorbed energy is read and divided by the cross-sectional area to calculate strength.
- 7The fracture type (complete, partial, unbroken) is recorded.
Izod Impact Acceptance Criteria
The method standard defines how the test is performed, not what the result should be. The acceptance limit comes from the material standard, the product specification or the customer's technical drawing; this page therefore gives no numerical limit.
Evaluation of Results
The result is reported in kJ/m² together with the fracture type. Specimens that do not fracture completely are reported separately; whether they are included in the average is determined by the standard.
Izod Impact Report
- Specimen identification, material type and cast/batch number, if any
- Specimen geometry, dimensions and preparation method
- Standard and test conditions applied
- Test temperature and ambient conditions
- Measured values and calculated quantities
- Fracture surface or indentation photographs (where applicable)
- Measurement uncertainty (if requested)
- A statement that the result applies only to the specimen submitted for testing
Accreditation
EUROLAB holds internationally recognised accreditation obtained from accreditation bodies party to the IAF and ILAC multilateral recognition arrangements, under ISO/IEC 17025 for laboratory testing, ISO/IEC 17020 for inspection and surveillance, and ISO/IEC 17021-1 and ISO/IEC 17065 for system and product certification. This chain ensures the reports and certificates issued are accepted worldwide.
Whether this test can be offered within accredited scope depends on your product and the standard applied; since accreditation is method-based, the scope is confirmed in writing at the quotation stage.
Scope and authorisationsRelated Regulations
- EN 10204 (inspection documents for metallic products)
- EU 305/2011 Construction Products Regulation (for products used in construction)
- Harmonised standards applied according to the product family
Mekanik Testler — What Does This Testing Field Cover?
The section below describes the field that the Izod Impact test belongs to; the conditions and acceptance criteria of this particular test are given in the sections above. The scope specific to your product is confirmed in writing at the quotation stage.
Mechanical testing measures how a material or a part behaves under force. The family ranges from static loading (tension, compression, bending) to time-dependent behaviour (fatigue, creep), and from hardness and wear to fracture toughness.
What these tests have in common is that the result is reported as a MATERIAL PROPERTY. Yield strength or hardness is not a conformity decision; it is numerical data against which the design and the product standard will compare. Mechanical test reports are therefore usually an input to an engineering decision rather than to a product approval — material selection, safety factor, life prediction.
The distinction between static and dynamic behaviour is the key to understanding the field. A part may appear entirely unstressed under a static load yet break under repeated loading; fatigue fracture occurs at stresses well below the yield strength and gives no warning. For rotating, vibrating or cyclically loaded parts, a tensile test alone is therefore not sufficient evidence.
Test conditions determine the result, and this is critical for the readability of the report: specimen geometry, loading rate, temperature, conditioning and the gripping arrangement. The same material gives different values under different conditions. In plastics the rate effect is very pronounced, in metals the temperature effect; in composites the specimen orientation changes the result entirely.
Hardness is the most misused measurement in the field. Because it is fast, close to non-destructive and inexpensive, it is often used in place of strength. Conversion tables from hardness to strength exist, but they are APPROXIMATE and depend on the material group; using them as the sole evidence in material acceptance is wrong.
The fracture mechanics side requires a specific competence. Fracture toughness and fatigue crack growth rate measurements make it possible to calculate how long a cracked structure will last; they are the basis of damage-tolerant design in fields such as pressure equipment, aircraft structures and pipelines.
Method groups in this field
Static tests
Tension, compression, bending, shear and torsion. Yield and tensile strength, elongation and modulus of elasticity are obtained.
Impact tests
Charpy and Izod notch impact; the brittle-to-ductile transition behaviour of the material is determined as a function of temperature.
Hardness
Brinell, Vickers, Rockwell, Shore and micro hardness. Valuable for surface treatment depth and local differences in strength.
Fatigue
Force- and strain-controlled axial fatigue, fatigue in bending; S-N curves and the endurance limit.
Creep and stress relaxation
Behaviour under long-term load at high temperature; decisive for boiler, turbine and pressure equipment materials.
Fracture mechanics
Plane-strain fracture toughness, the J integral, CTOD and fatigue crack growth rate.
Wear and friction
Taber and rotating drum abrasion, coefficient of friction measurements.
Commonly confused in this field
- Calculating strength from hardness is approximate; it cannot be used as the sole evidence in material acceptance.
- Adequate static strength does not demonstrate fatigue strength; a cyclically loaded part requires a separate test.
- If test rate and temperature are not reported, the result cannot be compared — especially for polymers and composites.
- A test specimen and the actual part may not give the same value; moulding orientation, weld lines and differences in surface treatment all have an effect.
- A strength value given for a composite without stating the specimen orientation is meaningless.
- ASTM and ISO counterparts measure the same quantity but use different specimen geometries; the results are not treated as directly equivalent.
Which decisions these results support
- Design verification and material selection
- Incoming material control and supplier approval
- Meeting the mechanical requirements of the product standard
- Failure analysis, life prediction and damage tolerance calculation
- Verifying heat treatment and surface treatment processes
Related Tests
Frequently Asked Questions About Izod Impact
Can an unnotched test also be performed?
Yes, standards also define an unnotched option. Comparing notched and unnotched results gives information on the material's notch sensitivity.
Why do different results occur for the same material?
Injection conditions, flow direction, notch sharpness and conditioning humidity markedly affect impact strength. Comparison is therefore only meaningful between specimens prepared under the same conditions.