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The Izod Impact Test Procedure and Sample Preparation

One of the most common tests, at least in the United States, of the physical characteristics of plastic materials is the notched izod impact test as specified by ASTM D256 Standard Test Method for Determining the Izod Pendulum Impact Resistance of Plastics.

How the Izod Impact Test Works

The Izod impact test fixes one end of a notched specimen in a cantilever position by means of a vice. A striker on the arm of a pendulum or similar energy carrier then strikes the specimen. The energy absorbed by the specimen in the breaking process is known as the breaking energy. The breaking energy can be converted into an indication of a materials impact resistance using such units as foot-pounds or joules.

Figure 1. Close up of notched specimen about to undergo an Izod impact test.

Izod Impact Test Data

While use of the data generated from a test for designing a part is not necessarily recommended, it still provides reasonable service as a quality control tool. Most US resin manufacturers have years of izod test data and many customers are accustomed to selecting product based on the data. So, love it or hate it, it appears that the impact…

Izod Tests - Determination of Impact Energy Using the Izod Test

Impact Tests

Impact tests are designed to measure the resistance to failure of a material to a suddenly applied force such as collision, falling object or instantaneous blow. The test measures the impact energy, or the energy absorbed prior to fracture. The most common methods of measuring impact energy are the:

•         Charpy Test

•         Izod Test

What is Impact Energy

Impact energy is a measure of the work done to fracture a test specimen.

When the striker impacts the specimen, the specimen will absorb energy until it yields. At this point, the specimen will begin to undergo plastic deformation at the notch. The test specimen continues to absorb energy and work hardens at the plastic zone at the notch. When the specimen can absorb no more energy, fracture occurs.

Brittle materials generally have lower impact stregths, while those registering higher impact strengths tend to to be tougher.

The Izod Test

The Izod test is has become the standard testing procedure for comparing the impact resistances of plastics. While being the standard for plastics it is also used on other materials.