The single-tongue tear strength test, also known as the trouser test or single-rip method, measures a fabric's resistance to the propagation of an existing tear and is one of the most widely used quality indicators for woven textiles. The method is standardized in ISO 13937-2, GB/T 3917.2, and ASTM D2261 and is routinely performed in accredited third-party laboratories for apparel, workwear, outdoor, and technical fabric verification. This article explains the test principle, specimen requirements, equipment, step-by-step procedure, result calculation, and typical applications of single-tongue tear strength testing.
Technical Overview
Tear strength describes the ability of a fabric to resist the growth of a cut, nick, or snag when a pulling force is applied. Unlike tensile strength, which measures the force needed to break a full strip of fabric across its entire width, tear strength reflects what happens after localized damage has already occurred: yarns near the tip of the cut are loaded one by one and rupture in sequence. For garments, tents, protective clothing, and industrial textiles, tearing resistance is often the more realistic predictor of service durability.
In the single-tongue method, a rectangular specimen is slit for a defined length from the center of one short edge, dividing that end into two equal legs or "tongues." Each leg is clamped in a separate jaw of a constant-rate-of-extension (CRE) tensile testing machine. As the jaws separate, the tear propagates along the line of the initial cut, and the force required to continue tearing is recorded as a force–extension curve, typically showing a sawtooth pattern of peaks corresponding to successive yarn breakage.
The single-tongue (trouser) tear procedure is governed by several equivalent or closely related standards:
- ISO 13937-2 — Textiles, tear properties of fabrics, Part 2: determination of tear force by the trouser test
- GB/T 3917.2 — the Chinese national standard, technically consistent with ISO 13937-2
- EN ISO 13937-2 and its national adoptions such as BS EN ISO 13937-2 and DIN EN ISO 13937-2
- ASTM D2261 — tearing strength of fabrics by the tongue (single rip) procedure using a CRE tensile testing machine
- Related tongue-type tearing procedures for woven fabrics are also covered within JIS L 1096
Results are expressed in newtons (N) and are reported separately for each principal direction of the fabric, since tear resistance along the warp and weft can differ substantially.
Testing Samples
Apparel and Fashion Fabrics
Woven fabrics such as denim, canvas, twill, gabardine, poplin, and oxford shirting are frequently evaluated because seams, pockets, and stress points are vulnerable to snag-induced tearing during wear and laundering. Heavier bottom-weight fabrics and uniform fabrics are among the most common submissions.
Workwear, Outdoor, and Military Textiles
Fabrics for coveralls, tents, awnings, sails, backpacks, and load-bearing equipment are commonly specified with minimum tear force requirements. Ripstop constructions, which are engineered specifically to arrest tear propagation, are routinely verified using this method.
Coated, Laminated, and Finished Fabrics
PU- or PVC-coated fabrics, laminates, and resin-finished woven fabrics can be tested to quantify how coating weight, binder content, or finishing chemistry affects tear resistance. Stiff coatings often reduce tear force, and the single-tongue method provides a sensitive means of tracking these changes.
Suitability Limitations
The method is intended primarily for woven fabrics. It is generally not suitable for knitted or highly elastic fabrics, and loose open weaves may fail by yarn slippage rather than yarn breakage. Nonwoven materials are normally assessed with trapezoid or pendulum-type methods instead. When threads slip out of the specimen instead of tearing, the result is invalid and an alternative method should be considered.
Testing Items
A standard single-tongue tear strength report from an accredited third-party laboratory typically includes the following items:
- Tear force in the warp (lengthwise) direction and tear force in the weft (crosswise) direction, in newtons
- The statistical value required by the selected standard, such as the median tear force per ISO 13937-2 or the average tear strength per ASTM D2261
- Individual specimen values, maximum and minimum values, and, where applicable, the coefficient of variation
- Number of specimens tested and the number discarded as invalid, with reasons
- The test standard and edition used, conditioning atmosphere, and any deviations from the standard method
Testing Methods
Test Principle
A centrally slit rectangular specimen is mounted with one leg in the upper clamp and one leg in the lower clamp of a CRE tensile tester. The legs are pulled apart at a constant rate, and the tear is propagated along the direction of the initial cut. The force–extension curve is recorded, and the characteristic peak forces produced as individual yarns or yarn groups rupture are evaluated to derive the tear force.
Apparatus and Calibration
The essential equipment comprises a CRE tensile testing machine with an appropriate calibrated force range, suitably sized parallel clamps with sufficient jaw pressure to prevent specimen slippage without jaw breaks, and a data acquisition system capable of resolving individual tear peaks. Cutting dies, templates, and a conditioned laboratory atmosphere (typically 20 ± 2 °C and 65 ± 4 % relative humidity per ISO 139) are also required. Force transducers and extension indicators must be verified against traceable calibration references before testing campaigns.
Specimen Preparation and Conditioning
Specimen requirements differ slightly between standard systems:
- ISO 13937-2 and GB/T 3917.2: rectangular specimens of 200 mm length and 50 mm width, with a 100 mm cut made along the center line from the middle of one short edge, forming two legs each 25 mm wide; a minimum of five specimens in each principal direction is customary
- ASTM D2261: comparable rectangular tongue specimens of 75 mm width and 200 mm length with a central slit of the length specified in the current edition of the standard
- Specimens must be cut representative of the full fabric width, free of creases, folds, and visible defects, and must not share the same lengthwise yarn groups where practicable
- All specimens are conditioned to moisture equilibrium in the standard atmosphere before testing, commonly for a minimum of 16 to 24 hours
Test Procedure
- Set the gauge length, for example 100 mm under ISO 13937-2, and the crosshead speed, for example 100 mm/min, as specified by the applicable standard
- Clamp one leg of the slit specimen in the upper jaw and the other leg in the lower jaw, keeping both legs aligned in the same plane and free of twisting or excessive pre-tension
- Start the machine and allow the tear to propagate along the line of the initial cut until the required tear length has been achieved
- Record the complete force–extension curve, then return the crosshead and remove the specimen
- Repeat for all remaining specimens in that direction, then test the second direction using correctly oriented specimens
- Discard and replace any specimen that tears transversely toward the specimen edge, tears at the jaw line, or fails by yarn slippage rather than yarn rupture
Calculation and Expression of Results
Under ISO 13937-2 and GB/T 3917.2, the tear force of an individual specimen is taken as the mean of the peak forces observed within the tear propagation zone, excluding the initial and final portions of the curve where tear initiation and end effects distort the readings. The result reported for the laboratory sample is the median of the valid specimen values, together with the coefficient of variation. Under ASTM D2261, the reported tearing strength is either the maximum force for single-peak fabrics or the average of the five highest peak forces for multi-peak tear profiles, averaged across the valid specimens. Results are always expressed in newtons and identified by test direction.
Factors Influencing Results
Tear force is strongly affected by yarn count, twist, and fiber type; weave density and interlacing pattern; the presence and rigidity of coatings, binders, or resin finishes; and moisture conditioning. Test-side variables such as specimen alignment, jaw pressure, gauge length, crosshead speed, and correct identification of the tear propagation zone also influence the outcome, which is why strict adherence to the stated standard is essential for interlaboratory comparability.
Applications
Single-tongue tear strength data supports a wide range of industrial decisions:
- Incoming fabric inspection and mill quality control against agreed minimum tear force specifications
- Product development, including the engineering of ripstop structures and the balancing of tear resistance against tensile strength, abrasion resistance, and stiffness
- Evaluation of the effects of dyeing, finishing, resin treatment, coating, and repeated laundering on fabric integrity
- Compliance verification for workwear, military, outdoor, and contractual procurement specifications that cite a defined tear force minimum
- Failure analysis when fabrics develop or propagate tears in service or in conversion
Because the method produces a full force–extension record, it is also valuable in research settings where the shape of the tear curve, not merely a single value, characterizes fabric behavior.
FAQ
What is the difference between the single-tongue test and the Elmendorf pendulum test?
The single-tongue test uses a CRE tensile machine and propagates a tear at a controlled rate along a slit, providing a detailed force–extension curve. The Elmendorf method uses a falling pendulum to deliver a rapid tearing energy to a smaller specimen and reports a tearing force derived from energy loss. The two methods measure related but distinct responses and their results are not interchangeable.
How many specimens are required?
A minimum of five valid specimens in each principal direction is normally tested, cut from different positions across the fabric width. Additional specimens are prepared when individual results must be rejected as invalid.
Why are warp and weft results reported separately?
Woven fabrics are anisotropic: yarn characteristics and crimp differ between the warp and weft systems, so tear resistance differs by direction. Purchasing specifications normally set separate minimum values for each direction.
What causes a specimen to be rejected?
Common rejection criteria include the tear running markedly off the line of the cut toward the specimen edge, tearing at or slipping from the jaws, and failure by yarn slippage rather than yarn breakage. If invalid results recur, the method may be unsuitable for that fabric.
Are ISO 13937-2 and ASTM D2261 results comparable?
Both are single-rip CRE procedures, but they differ in specimen geometry, tearing distance, and the statistical calculation of the reported value. Results should not be compared directly across methods; the report must always identify the standard used.
Is there a universal pass or fail limit?
No. Acceptance levels are set by the buyer, brand, or end-use specification. Robust workwear and outdoor fabrics are commonly specified with minimum tear forces in the range of roughly 15 N to 30 N or higher, while lightweight apparel fabrics may carry lower requirements. Accredited third-party laboratories report the measured values against the applicable specification rather than issuing a universal pass threshold.