Tear resistance is generally desired for all fabrics. It is especially important for fabrics used in outerwear, shirting and technical fabrics. (TS EN ISO 13937-1, TS 1998/8217, TS EN ISO 13937-2, TS EN ISO 13937-3, TS EN ISO13937-4, ASTMD 1424) Generally, a torn garment or fabric loses its importance for the wearer. For these reasons, fabrics are tested for tear strength.
Tear strength of woven fabrics can be determined using different methods such as tongue method, trouser method, wing method and ballistic pendulum method.
Ballistic pendulum (Elmendorf) method
According to this method, the tear strength is determined according to the standard 'TS EN ISO 13937-1 Tear Properties of Textiles- Fabrics - Part 1: Determination of Tear Force by Ballistic Pendulum Method'.
This method covers the process of measuring the tearing force required to progress from a tear in the fabric to a single tear of a certain length when a sudden force is applied.
Used materials
Standard atmospheric conditions
Tear strength tester (Pendulum tester)
laceration template
Scissors
Test samples.
Pendulum test device features;
The device has two fixed and movable jaws.
The fixed jaw is attached to the device base, and the movable jaw is attached to a pendulum that can freely swing downwards with the effect of gravity.
The test sample is placed between these two jaws.
These jaws are 3 mm + _0,5 mm apart to allow a sharp blade to pass between them.
The pendulum is in the form of a circle segment and has the highest potential energy when it is in its initial position, and the fixed and movable jaws are in alignment.
The mass of the pendulum can be adjusted by adding mass or changing the pendulums.
Pendulums with 4 different weights can be attached to this device.
Capacity increase in mechanical devices is provided by masses in the shape of a circle added to the pendulum.
A heavier pendulum provides more force during testing.
The device may be of mechanical or electronic type.
Elmendorf device load capacities
Pendulum Tear strength capacity (mN)
A-Light 8000
B-Medium 16000
C-Heavy 32000
D-Extra heavy 64000
A rigid frame supports the pendulum and a fixed jaw, a blade for cutting the tear, and a measuring device. This frame has a spirit level.
Sample preparation
For the preparation of the test pieces, a mold of dimensions (shown below) is prepared.
This pattern is placed on the sample fabric and the test pieces are marked in the weft and warp directions.
While the test is being cut, the lower edge of the sample mold is placed parallel to the threads that will be subjected to the force.
As can be seen below, test samples are prepared with a length of 100 ± 2 mm and a width of 75 ± 2 mm.
For the warp direction, the short side of the sample should be taken parallel to the weft yarns, for the weft direction, parallel to the warp yarns.
A 20 ± 0.5 mm notch is made in the lower middle part of the sample.
This notch can be made with the blade of the instrument after the specimen has been placed on the instrument.
The tear length is 43 ± 0.5 mm long.
The test pieces are cut in such a way that they do not contain the same weft and warp as shown below.
Experimental Procedure
First, the prepared test samples are conditioned.
Then, the pendulum weights are selected according to the sample type.
Each pendulum weight has a control weight.
For the experiment, these two weight groups are placed together in the device.
It is adjusted according to the capacity of the device to be between 20% and 80% of the tear measurement scale.
The pendulum arm of the device is lifted to the starting point with the maximum potential energy.
Meanwhile, the fixed gripper jaw and the movable jaw on the pendulum align.
The test piece is centered so that its long sides are parallel to the upper edge of the gripper jaws and placed between the clamps.
With the knife on the device, a 20 mm long notch is made on the test piece.
The pendulum is then released and the test piece is completely ruptured by the separation of the movable jaw from the fixed jaw.
The tearing force is read from the display in newton units.
The test is repeated on at least 5 test samples for each fabric direction.
Also, care is taken to ensure that the tear in the test piece is completed, that it remains within 15 mm of the notched area, that there is no thread slipping from the fabric and that there is no slippage in the jaw.
