Tear Test

Introduction:

The tear test applies a force to a material that already contains a partial fracture or rupture

otherwise known as a “tear” in order to bring the material to complete failure. This is done by

placing the test sample into a tensile testing or universal test machine so that the section on one

side of the fracture is pulled up and the section on the other side is pulled down. Then a steady load

is applied until the tear has propagated through the entirety of the sample and the two sections have

been completely separated from one another.

Purpose of a tear test:

The tear test goal is to determine a material’s ability of resisting the growth of the initial tear

or its “tear resistance”. The value of a material’s tear resistance is generally accepted to be the

force required to complete the tear so that it has gone completely though the material so that it has

been separated into two sections. For using flexible materials they may suffer a partial rupture

intentionally or otherwise, so this tear characteristic is particularly important to applications.

Types of tear tests:

Most tear resistance tests are taken commonly one of three forms. These forms differ from one another

in the configuration and preparation of the test sample, the grip placement, and the speed of

testing.

The first form is as the trouser shape tear test and involves a rectangular sample that has a cut down

the middle of one half of the sample so that two legs are formed and the sample resembles a pair of

trousers. Each leg is then placed into one of the test grips and is then pulled apart so that the tear

continues down the middle of the sample.

The second form is as tongue tear test requiring the sample have a tab cut in the middle. This tab is

cut so that so that it is separated the rest of the sample on the bottom and sides but not the top.

The tab is then placed in the top grip while the rest of the sample is placed in the bottom grip. As

the top grip is moved upward and the tab is pulled so that the cuts on both sides are extended upward

to the top of the sample, and the tab is eventually pulled free leaving a rectangular piece in the top

grip and a “U” shaped piece in the bottom.

Finally it’s the trapezoid tear test. The test sample is cut into the form of an isosceles trapezoid

with a small cut made in one side. The sample is then loaded into the test fixture so that the tear

made by the cut will propagate as the grips move apart. Generally in order to make the tear extends

horizontally the sample is orientated.

Types of materials for tear testing:

The more common materials that benefit from tear testing are textiles, fabrics, elastomers, rubbers,

polymers, packaging and paper products.

These are flexible materials as they are more susceptible to accidental fractures and punctures as

well as partial ruptures (tears and holes). Each of these materials can have serve in a wide range of

industries such as clothing, medical, biomedical, and dental.

Standards