Testing on Threads, Yarns, and Twine

EN ISO 2062, EN 12562, DIN 53835-2, -3, ISO 11566

The physical characteristics of these primary textiles are mainly determined by tensile tests, with specimen preparation as specified by the relevant standard.

Zwick has the ideal testing machines and extensometers for textile testing and—most importantly—the correct specimen grips and jaw inserts, guaranteeing reliable test sequences.

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Tensile Tests on Sewing Thread According to EN ISO 2062

Tensile tests on sewing thread are carried out according to EN ISO 2062. In this example, screw grips are used and the strain is measured via the crosshead travel, with results shown in a typical force-strain diagram.

The grip-to-grip separation is 250 mm or 500 mm. The test speed is dependent on the grip-to-grip separation. With 250 mm grip-to-grip separation a 250 mm/min is used and with 500 mm grip-to-grip separation the required 500 mm/min. The maximum tensile force and the maximum strain are determined.

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Tensile Tests on Aramid Yarn According to EN ISO 12562

Tensile tests on aramid yarn are carried out according to EN ISO 12562. Deflection specimen grips are used, with results shown in a typical force-strain diagram.

The force reduction curve enables defined grip-to-grip separation during the test; thus direct extension measurement is not necessary during the test.

The force reduction curve reduces the tensile strength before end clamping. The specimen is held securely preventing jaw breaks. and the test is performed according to the standard. The specimen should break in the free clamping length and not in the deflectors.

An extension measuring system is used for higher measurement accuracy without clamping influence. A mechanical measuring system should be used only when the risk of damage at specimen break does not exist.

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Elastic Behavior of Elastic Yarn According to DIN 53835-2, -3

According to this standard, the test is used to evaluate the elastic behavior of monofilaments of elastofibers by repeated tensile load between constant offset yields. This standard is applicable to all filament yarns made from elastic yarn that have more than 300% elongation.

Tests on elastic yarns (in this case 0% to 300% elongation with a grip-to-grip separation of 100 mm) are loaded with 5 cycles not until break but between defined offset yields. The specimen is moved 500 mm/min between the point of load application (300% elongation) and the point of load removal. To not distort the results there should be no delay at the reversal points.

The residual force is determined in the 5th cycle and the remaining strain as well as the deformation of the elastic yarn is determined. In this example, spring screw grips are used for the test with elongation measured via crosshead travel and results shown in a typical force-strain diagram.

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Tensile Test on 2-Ply Thread According to EN ISO 2062

Pneumatic capstan grips are used when testing 2-ply thread according to EN ISO 2062, with elongation measured via crosshead travel. The results are shown in a typical force-strain diagram. Due to the radii of the deflectors, a clamping length of 500 mm must be used.

The force reduction curve enables defined grip-to-grip separation during the test; thus direct extension measurement is not necessary during the test.

The force reduction curve reduces the tensile strength before end clamping. The specimen is held securely preventing jaw breaks and the test is performed according to the standard. The specimen should break in the free clamping length and not in the deflectors.

An extension measuring system is used for higher measurement accuracy without clamping influence. A mechanical measuring system should be used only when the risk of damage at specimen break does not exist.

DIN EN ISO 2062 rope 25kN

Tensile Test on Multi-Filament Thread According to EN ISO 2062

Multi-filament thread, with its smooth texture and tendency to twist, places extra demands on test arrangements. In this case the material is held in rope grips and elongation is measured via an optical long-travel measuring system because the crosshead travel reference value for the strain cannot be precisely defined. Standard EN ISO 2062 also applies to this test.

The gripping force of this specimen grip is generated via looping and additional screw, wedge, or hydraulic end clamping. Due to the single or multiple looping on the load reduction roller the tensile stress is significantly relieved by frictional contact. A roller diameter between Ø 30 mm – Ø 250 mm is used depending on the material used.

Tensile Tests on Monofilaments According to ISO 11566

For monofilaments tests according to ISO 11566, individual fibers from carbon-based multifilament fabrics or staple fibers are tested. A paper frame enables the specimen to be clamped in the spring screw grip as shown. Monofilaments are very small and extremely sensitive to gripping as well as very difficult to handle. For this reason the paper frame, which is prepared with a centered defined hole, is used as reinforcement. The filament is glued to the paper frame. Once the glue is dry the specimen can be clamped in the specimen grip. The paper frame is cut prior to the test. Very small loads ranging from 0.04 – 5 N could occur. Elongation is determined via crosshead travel.
Single filaments
Tensile test on Rowings BISFAPH

Tensile Tests on Rovings

Roving is clamped in a 270° capstan grip and tested until break, with results shown in a typical force-displacement diagram.

The force reduction curve reduces the tensile strength before end clamping. The specimen is held securely preventing jaw breaks. Tests are performed according to the standard. The specimen should break in the free clamping length and not in the deflectors.

An extension measuring system must be used for higher measurement accuracy without clamping influence. A mechanical measuring system should be used only when the risk of damage at specimen break does not exist. In most cases an optical measuring system is used.

Double capstan grips

Tensile Tests with Double Capstan Grips

With this deflection principle there is a two-step force gradient, resulting in a specimen break at gage length without sliding of the specimen on the lower roller and without jaw breaks. A simple tensile test is used for calculating the maximum force and maximum strain. The results are shown in a typical force-strain diagram.

With the double capstan grip the specimen is placed on the roller connected to the load cell in the form of a sling. The specimen is then guided over a lower roller and again over a height-adjustable third roller. After the defection of the double thread, a defined pretension weight is attached. During this phase all three rollers are moving in order to balance the extensions which are created by the attachment of the pretension weight.

The three lengths are adjusted to the material being tested. Finally, the double thread is clamped in the height-adjustable specimen grip.

After the specimen grip closes the deflection rollers are locked, thereby creating frictional forces between the rollers and the specimen preventing the specimen from slipping. The roller diameter is dimensioned in such a way that the occurring friction does not influence the test results.

Since the materials to be tested often slip out of the clamping area, a specimen grip with constant gripping force is used.

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