Tear Strength

► It is a property of textile material to withstand the effect

of tearing or resistance to propagation of tear after it has
been initiated.
► Tearing of a fabric can occur in a wide range of products
and is involved in fatigue and abrasion processes as well
as the catastrophic growth of a cut on application of a
force.
► A tear strength test is often required for woven fabrics
used for applications including army clothing, tenting,
sails, umbrellas and hammocks. It may also be used for
coated fabrics to evaluate brittleness and serviceability.
Methods for testing tear strength
► The following methods are in use or being developed:
trouser or single tear, double or tongue tear, wing tear,
trapezoidal tear, ballistic pendulum (Elmendorf), puncture
or snag tear, tack tear, and wounded burst tear.
► ISO 13937-1-2000 Textiles – Tear properties of fabrics –
Part 1: Determination of tear force using the ballistic
pendulum method (Elmendorf)
► ISO 4674-1998, part 1: Determination of tear resistance
► ISO 13937-3-2000 Textiles – Tear properties of fabrics –
Part 3: Determination of tear force of wing-shaped test
specimens
► EN 1875-3 Determination of tear resistance – Part 3:
Trapezoid tear, 1997
► ASTM D1423-83 Tear resistance of woven fabrics by falling
pendulum (Elmendorf)
Sample preparation for tear test
Devices for tearing tests

► Two devices have been commonly used for tearing tests:

1. Elmendorf tearing tester and
2. CRE tester
Principle of Elmendorf tear testing
machine
► The falling (ballistic) pendulum (Elmendorf) method is used for the
determination of the average force required to continue or propagate a single
rip-type tear starting from a cut in a woven fabric by means of a falling
pendulum (Elmendorf) apparatus.
► Part of the energy stored in the pendulum is used to produce the tearing (and
any deformation of the test piece). The magnitude of this is indicated by the
energy lost compared to the energy of the falling pendulum without a test
piece in place.
► The weight attached to the pendulum can be selected based on the fabric
tested and the standard used.
► The basic characteristics of this test are that stresses are applied by
subjecting the test piece to a sudden blow; hence the test speed (strain rate)
is relatively high compared to that of a CRE machine.
► This method is not suitable for knitted fabrics, felts or non-woven fabrics. It
is applicable to treated and untreated woven fabrics, including those heavily
sized, coated or resin treated.
Procedure of tear testing by Elmendorf tear
tester
► The apparatus to perform this consists of a fixed jaw, a moveable jaw, a
pointer, and a pendulum. This apparatus as a whole is known as Elmendorf
Tear Tester.
► A sample of a specific dimension is placed between the fixed jaw and the
moveable jaw.
► An initial slit along the sample is created either by a cutter mounted on the
fixed jaw or by using a manual cutter.
► The sample is torn between the fixed distances and resistance to tearing is
noted.
► The dimension of the testing sample is 100 × 63.5 mm. The pendulum and
pointer are brought to their starting position and the sample is placed in the
jaws. A slit of 20 mm is created along the width of the fabric. The pendulum
is released and the reading is noted. The experiment is performed five
times and the average of the five readings is taken.
The constant-rate-of-extension tear tester
► The tear test can be performed on a normal tensile instrument. For the
tongue method a rectangular specimen is cut in the centre of the shorter
edge to form two ‘tongues’ (or ‘tails’).
► Each tongue is gripped in the clamps of a constant-rate-of-extension (CRE)
machine and pulled to simulate a rip.
► The force to continue the tear is calculated from readings as the average
force to tear.
► The force registered in a tear test is irregular. The reading represents the
force required for tear initiation, the subsequent reading being the force to
propagate the tear.
► For a woven fabric, the average of the warp and weft direction tests is given
as the result.
► The tearing force can rise rapidly; therefore the response characteristics of
the apparatus are particularly important. The rate of tear is normally 100
mm/min.
Factors affecting tear strength
► The first is the number of yarns that are going to bear the load; as the number of
yarns per inch increases, tear strength decreases, and vice versa.
► The second factor that affects the tear strength of a fabric is the amount of yarn
slippage in the fabric structure; this is related to the weave design:
▪ Fabric with a longer float tends to have a higher tear strength as compared to
fabric with a shorter float.
▪ For instance, plain weave, which has the maximum amount of interlacement, has
the least tear strength because, when the tear force is applied only one yarn
bears the load, whereas in twill weave there is a greater float and when force is
applied the yarn starts to slip and work as a unit to bear the load, hence greater
force is born by the fabric.
⮚ Tear strength is also affected by fiber type, yarn type, the GSM of the fabric, and
the type of finish applied to the fabric.
⮚ A tightly mounted fabric is easier to tear than a slackly mounted fabric because
the tear force propagates from yarn to yarn as the linear force in the yarn
restricts yarn slide.
⮚ Tear resistance can also be affected considerably by the speed of the test.