Mechanical & Physical

Izod impact strength

Pendulum impact test on notched plastic bars

Izod testing swings a pendulum into a notched bar clamped upright and measures the energy absorbed as it breaks. It is a quick, standard way to compare the toughness of plastics and composites.

1 test optionASTM D256 / ISO 180Pendulums ~1–22 JTypical turnaround 5–7 working days
Request this test WhatsApp about Izod impact strength
Izod impact strength measurement principleIllustrative
Energy scalePendulumStrikerNotched specimenViseEnergy absorbed
One swing, one breakIllustrative
01 / Overview

What is Izod impact strength?

In an Izod test a standard bar is clamped upright as a cantilever, with a V-notch facing the striker. A pendulum released from a fixed height hits the bar above the notch; how far it swings on after the break shows how much energy the fracture absorbed.

The result, in J/m of notch width (ASTM D256) or kJ/m² of cross-section (ISO 180), ranks how brittle or tough a material is under a sudden blow. Unlike a slow tensile test, it captures notch sensitivity at high strain rate, which is why it is widely used for grade selection and quality control.

02 / How it works

How it works

  1. 01

    Bar is notched

    A standard bar is moulded or machined, given a precise V-notch and conditioned.

  2. 02

    Bar is clamped

    The bar is held upright in a vise, notch facing the pendulum and level with the jaws.

  3. 03

    Pendulum strikes

    The pendulum is released from a fixed height and breaks the bar in a single blow.

  4. 04

    Energy is read

    The height of the follow-through swing gives the energy absorbed by the break.

03 / What it measures

What it measures

Notched impact strength

Energy to break a notched bar, per notch width or cross-section.

Useful forGrade selection, incoming quality control

Unnotched impact strength

Toughness of a plain bar with no stress-raising notch.

Useful forFilled compounds, composites, recycled blends

Break type

Complete, hinge, partial or no break, as the standard defines them.

Useful forTelling brittle from ductile behaviour

Notch sensitivity

Compare notched and unnotched results to see how much a notch weakens the part.

Useful forParts with sharp corners, ribs and snap-fits

Formulation comparison

Rank grades, fillers, modifiers or process changes by impact energy.

Useful forCompounding and formulation development
04 / Test options

Choose the Izod impact strength options you need

1 option · none added yet

Izod impact strength test options
05 / Sample requirements

Sample requirements

Accepted forms
Moulded or machined bars; sheets or plaques the lab can cut to size
Specimen size
80 × 10 × 4 mm (ISO 180) or 63.5 × 12.7 mm, 3–12.7 mm thick (ASTM D256)
Quantity
At least 10 bars per sample, including spares
Notching
Send pre-notched bars, or ask the lab to notch them
Standard
State ASTM D256 or ISO 180, notched or unnotched
  • Bars flat, straight and free of voids, sink marks or flash
  • Label each sample and mark the moulding or flow direction
  • State the standard, notch type and any conditioning needed
  • No cracked, warped or visibly damaged bars
  • No metal specimens without discussing first

Hazardous or air-sensitive samples: mention it in your request, and attach the MSDS if you have one.

06 / Results & turnaround

Results & turnaround

What you receive

  • Impact strength per bar (J/m or kJ/m²)
  • Mean and standard deviation
  • Break type for each bar
  • Test details: standard, pendulum energy, notch
  • Report PDF

Turnaround & pricing

Typically 5–7 working days after samples reach the lab.

Price confirmed in your quotation, depending on user type, options and number of samples.

Sample report · IllustrativeExample notched Izod38 J/mIllustrative — not measured sample data
07 / Limitations

When Izod impact strength isn't the right fit

Let’s find your next step

Need help choosing an option?

Share what you want to measure. We’ll help you find the right next step.

Share your requirement WhatsApp RNDgrid