Tear

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Tear strength and tear resistance need to be measured, not only to make sure a product doesn't unintentionally rip but also to verify it does actually tear where it is intended, e.g. along a crease or perforation.

In some materials, a tear will propagate rapidly, predictably or evenly. In other materials, it will be more unpredictable.

Tear testing methods set standard conditions under which a product or material specimen can be measured in a repeatable way. Usually, the tear is initiated with a cut or notch in the specimen, which is held at each end by tensile grips. The material is torn at a constant rate of extension (CRE) to ensure optimum repeatability and the maximum peak tensile force is recorded.

There are various methods of tear testing but they all require both ends of the material specimen to be held in tensile grips and to be torn apart. The tensile force-extension values are continuously recorded to obtain precise data for calculating tear values. The main differences between the methods are the specimen shapes and the angle of tear.

Trouser tear (single rip) - single cut along centreline; used for fabric testing 'across warp' or 'across weft'
Tongue tear (double rip) - double cut about the centreline; used for fabric testing 'across warp' or 'across weft'
Wing tear (Graves) - die-cut sample with 90° angle at the centre; used for measuring the initial tear in flexible plastic films
Wing tear (Winkelmann) - a crescent-shaped sample with a razor-nick at the centre; used for measuring the initial tear in flexible plastic films
Trapezoidal tear - trapezoid shaped sample with a small cut at one side; used to test fabric resistance against sharp object e.g. nail or screw
Baumann tear - slit cut laterally in the centre of sample; used to test the tear strength of leather
Delft tear - slit cut laterally in the centre of the sample; used to test the tear strength of vulcanised and thermoplastic rubbers

Some tear test methods use a falling pendulum to create impact, but most apply a tensile force, for which Mecmesin meets these standards with its range of universal testers.