The Notched Izod Impact test is a recognized standard of the American Society for Testing and Materials for testing impact strength of a material. This next blog series we want to focus in on different impact tests used in the industry to test material impact resistance.
Why is it important to test impact strength?
Knowing the impact resistance of a material can help the engineer decide the best material to fit the project goals. Consider the importance of needing to know the impact strength of a product the plastic portion of a car bumper. One can expect this bumper to undergo some obvious wear and tear. As an example, debris from the road might pop up and hit the bumper while driving. Under these conditions, the plastic material ought to be strong enough to withstand this sort of impact applied to the bumper without breaking. The question we are asking is, how tough is the material when absorbing energy during plastic deformation? The more brittle the material, the lower the impact toughness.
What is the Notched Izod Impact test?
There are a lot of different impact tests, as mentioned previously. Using a pendulum swing and a single point of contact for the material, the Notched Izod Impact test is defined as “kinetic energy needed to initiate fracture and continue the fracture until the specimen is broken.”1
How to use the Notched Izod Impact test:
The material/specimen is clamped into the Izod Impact testing mechanism with the notched side facing the hammered edge of the pendulum. When the pendulum is released the hammer swings down and strikes the material. Upon impact, if the specimen does not break, more weight is added to the hammer until the point of breakage is reached. Since thermoplastics toughness can change depending on the temperature of the environment, sometimes in testing a material it is wise of the engineer to simulate the environment of the intended purpose of the material while performing the Notched Izod Impact test. The resulting impact strength is measured in impact energy in J divided by the thickness of the specimen. The final result is typically averaged of 5 different test specimens.