Tear Strength Testing: An In-Depth Analysis of Chinese National Standards (GB/T 3917 Series)

Tear strength is a decisive durability parameter for woven fabrics and technical textiles, measuring a material's ability to resist the propagation of an existing cut or tear. In China, tear performance is evaluated primarily under the GB/T 3917 national standard series, which specifies four instrument-based methods aligned with ISO 13937. This article analyzes the scope, specimen design, equipment, calculation, and application of these national standards, and compares them with international equivalents to help laboratories and quality teams select the correct test protocol.

Technical Overview

Tear strength, expressed as tear force in newtons (N), quantifies the resistance of a fabric to the continued propagation of a tear after it has been initiated. It is fundamentally different from tensile (breaking) strength: tensile testing measures the force needed to rupture an intact strip, whereas tear testing measures the force required to advance a deliberately cut or slit region through the remaining yarns. In real-world service, garments, tents, upholstery, and industrial textiles rarely fail from uniform tensile loading alone; failure typically begins with a snag, puncture, or localized cut, after which tear resistance determines whether the damage stays minor or propagates catastrophically.

In the Chinese national standard system, fabric tear properties are governed by the GB/T 3917 series, titled "Textiles - Tear properties of fabrics," whose current edition dates from 2009 and which replaced the original 1997 versions. The series consists of four parts, each corresponding to a distinct specimen geometry and instrument principle. The 2009 revision was developed as a modified adoption of the ISO 13937 series (2000 edition), which means the technical content is closely aligned with the corresponding international methods, and the series is also harmonized in Europe as EN ISO 13937. All tests are performed on fabric specimens conditioned to the standard atmosphere specified in GB/T 6529 (typically 20 ± 2 °C and 65 ± 4% relative humidity).

• GB/T 3917.1 - Determination of tear force using the ballistic pendulum method (Elmendorf type)
• GB/T 3917.2 - Determination of tear force of trouser-shaped test specimens (single tear method)
• GB/T 3917.3 - Determination of tear force of wing-shaped test specimens (single tear method)
• GB/T 3917.4 - Determination of tear force of tongue-shaped test specimens (double tear method)

Because each method imposes a different geometry on the tear zone, the numerical results are not interchangeable between parts of the series. Product standards, purchase contracts, and laboratory scopes of accreditation always identify the specific method to be used, and comparisons between suppliers or production lots are valid only when the same method, direction, and calculation convention are applied.

Testing Samples

Correct specimen preparation is the single largest source of variability in tear testing. Specimens must be cut from representative, undamaged areas of the fabric, well away from selvedges and cloth ends, and must be free of creases, folds, or visible defects. Templates or precision cutting dies are strongly recommended so that the slit geometry, width, and alignment are reproduced exactly. For each fabric, at least five valid specimens are required for each direction of interest, and additional specimens should be prepared when the fabric structure produces highly scattered results. All specimens must be conditioned in the standard atmosphere before testing.

Trouser-Shaped Specimens (GB/T 3917.2)

The trouser specimen is a rectangle, typically 200 mm long and 50 mm wide, with a central cut approximately 100 mm long made along the longitudinal axis from one end. This cut divides that end of the specimen into two equal "legs," each about 25 mm wide. During testing, one leg is gripped in the upper jaw and the other in the lower jaw, so that the tear advances along the centerline of the specimen. The trouser geometry is the most widely referenced method for apparel and general woven fabrics because it is simple to prepare and produces a clear tearing zone.

Wing-Shaped Specimens (GB/T 3917.3)

The wing specimen is a rectangular blank with two symmetrical angled cuts that form a pair of "wings" at a defined angle to the longitudinal axis. The jaws grip only the wings, which mechanically constrains the tear to propagate along the intended centerline. This geometry is intended for fabrics whose tear direction is unstable in the trouser test, such as fabrics in which the tear tends to deviate or turn. It delivers a single, controlled tear path and therefore reduces directional scatter.

Tongue-Shaped Specimens (GB/T 3917.4)

The tongue specimen is a rectangle with a defined slit cut parallel to the tearing direction, creating a central tongue section. The tongue is clamped in the upper jaw while the two remaining flanks of the fabric are held together in the lower jaw. As the jaws separate, the tear propagates simultaneously along both edges of the tongue, which is why the method is described as a double tear method. The averaging effect of two simultaneous tear fronts makes this geometry attractive for heavier, denser, or coated constructions.

Ballistic Pendulum Specimens (GB/T 3917.1)

Specimens for the pendulum (Elmendorf) method are short rectangles, typically about 100 mm long and 63 mm wide, with a short slit (about 20 mm) precut at the midpoint of one end. The two halves of the slit end are clamped, one on the fixed frame of the instrument and one on the pendulum arm; when the pendulum is released, it tears the remaining uncut length of the specimen, which corresponds to a defined tearing distance (commonly about 43 mm depending on the instrument). Because tear force is derived from the energy lost by the pendulum, this method is fast, economical, and especially suitable for routine quality control and lighter-weight fabrics.

Testing Items

The measured quantity in all four methods is the tear force, reported separately for each principal direction of the fabric. For woven fabrics the directions are the warp and weft; for nonwoven and directional technical fabrics they are the machine and cross directions. It is important to note that the direction designation refers to the direction in which the tear propagates, and the yarns being severed run perpendicular to that direction. Beyond the raw peak values, the standards define how derived statistics must be calculated and reported.

• Tear force in the warp direction (or machine direction) in newtons
• Tear force in the weft direction (or cross direction) in newtons
• Mean tear force calculated from valid peaks within the defined tearing zone
• Coefficient of variation and, where required, the 95% confidence interval of the mean
• Classification of tear behavior, including normal propagation, multi-directional tearing, yarn slippage from the jaws, and incomplete or invalid tears
• Number of specimens tested and number of rejected results with reasons for rejection

A tear is considered valid only when the tear propagates along the intended path for the intended distance. If the specimen tears across its width, slips out of the jaws, or the tear deviates into an unintended direction, the result is discarded, the event is recorded, and a replacement specimen is tested. High rejection rates are themselves diagnostic information, often indicating fabric anisotropy, loose weave structure, or unsuitability of the chosen method for that material.

Testing Methods

The GB/T 3917 series is built on two instrument families: falling-pendulum (Elmendorf) tear testers for Part 1, and constant-rate-of-extension (CRE) tensile testing machines for Parts 2, 3, and 4. CRE machines used for tear testing should meet the force accuracy requirements of the relevant calibration standards, and pendulum instruments must be verified for energy capacity and friction losses. Modern digital instruments automatically acquire the force-displacement curve, identify peaks, and compute statistics, but the analyst remains responsible for verifying that the tear occurred correctly.

Pendulum (Elmendorf) Method - GB/T 3917.1

The specimen is clamped, the pendulum is raised to its initial position, and it is then released. The kinetic energy of the falling pendulum tears the specimen through the defined tearing distance, and the energy absorbed is read from the instrument scale or sensor. Tear force is calculated by dividing the tearing energy by the tearing distance, with corrections applied for pendulum friction where required. Instruments are available with a range of capacities, from a few hundred millinewtons for light fabrics up to tens of newtons for heavy constructions, and the specimen or capacity must be chosen so the reading falls within the calibrated working range. Results are reported in newtons or millinewtons as the mean of at least five valid specimens per direction.

Trouser (Single Rip) Method - GB/T 3917.2

The two legs of the trouser specimen are gripped in the upper and lower jaws of a CRE machine, typically with a jaw separation of about 100 mm, and the jaws are separated at the specified speed of approximately 100 mm/min. As the tear advances, the force trace exhibits a series of peaks corresponding to successive yarn breakages. Peak forces occurring within the first and last few millimeters of the tearing zone are excluded, and the tear force is calculated as the mean of the remaining valid peaks. The method rewards yarn mobility, because yarns that can group together at the tear front produce higher tear resistance, which is why loose weaves often outperform tightly woven ones of similar yarn strength.

Wing (Single Rip) Method - GB/T 3917.3

The wing specimen is mounted so that only the wings are clamped in the jaws, and the test proceeds on a CRE machine at the specified separation speed, typically around 100 mm/min. The constrained geometry forces the tear to run along the centerline between the angled cuts, which stabilizes the tear direction in fabrics that behave erratically in the trouser test. Data reduction follows the same peak-analysis logic as the trouser method: valid peaks within the tearing zone are averaged to obtain the reported tear force.

Tongue (Double Rip) Method - GB/T 3917.4

The tongue specimen is mounted with the tongue in the upper jaw and the remainder of the fabric in the lower jaw, and the jaws are separated at the specified rate on a CRE machine. Because the tear advances along both sides of the tongue at the same time, the force trace reflects two simultaneous tear fronts, which tends to smooth the peak structure and reduce scatter. This method is frequently specified for heavier industrial fabrics, coated fabrics, and constructions where a single tear front gives unstable results.

Alignment with International Standards

Each part of GB/T 3917 corresponds to an international counterpart, which simplifies the transfer of specifications between Chinese and overseas supply chains:

• GB/T 3917.1 (pendulum) aligns with ISO 13937-1 and is technically comparable to ASTM D1424
• GB/T 3917.2 (trouser, single rip) aligns with ISO 13937-2
• GB/T 3917.3 (wing, single rip) aligns with ISO 13937-3
• GB/T 3917.4 (tongue, double rip) aligns with ISO 13937-4
• ASTM practice additionally includes the tongue single-rip method (ASTM D2261) and the trapezoid method (ASTM D5587), the latter being widely used for nonwovens and geotextiles; for geotextiles in the Chinese system, the trapezoid approach is covered by the dedicated GB/T 13763 standard

Although the GB/T and ISO methods are closely harmonized, small differences in wording, apparatus verification, and reporting requirements exist because GB/T 3917 is a modified rather than identical adoption. Laboratories performing acceptance testing for international contracts should confirm with the buyer whether GB/T, ISO, EN ISO, or ASTM results are required, and accredited third-party laboratories routinely maintain capabilities across all of these frameworks.

Applications

Tear strength data derived from the GB/T 3917 series underpin quality control, product development, and compliance activities across the entire textile value chain. The parameter is embedded as a minimum requirement in numerous product and procurement specifications, and it is one of the most frequently tested mechanical properties in accredited third-party laboratories serving textile exporters and domestic brands alike.

• Apparel: denim, workwear, uniforms, and military garments, where snag resistance and tear propagation control are essential for safety and service life
• Outdoor and sports equipment: tent fabrics, backpacks, sailcloth, and parachute materials exposed to abrasion, puncture, and wind loading
• Home and contract textiles: upholstery, mattress ticking, and bedding, where local damage must not spread during use
• Medical and protective textiles: surgical gowns, drapes, and protective clothing, where fabric integrity after accidental damage is critical
• Technical and industrial textiles: filter fabrics, conveyor belting, coated membranes, automotive interior materials, and geotextiles

For product engineers, tear results are also a development tool. Because tear resistance depends strongly on yarn mobility, weave density, yarn twist, and finishing chemistry, tear data are used to optimize fabric construction, evaluate resin or softener finishes, and qualify alternative fibers or suppliers. Comparative testing across the four GB/T 3917 methods can reveal whether a fabric's weakness lies in yarn strength or in tear-path stability, guiding targeted corrective action.

FAQ

What is the difference between tear strength and tensile strength?

Tensile strength measures the force required to break an intact strip of fabric under direct pulling, while tear strength measures the force required to continue a tear through a fabric that is already cut. The two properties respond differently to fabric design: a dense, tight construction raises tensile strength but often lowers tear strength because the yarns cannot bundle together at the tear front. Both tests are normally required for a complete picture of mechanical durability.

How do I choose among the four parts of GB/T 3917?

Follow the product standard or contract specification first, since it usually names the exact method. In the absence of a specified method, the pendulum method (Part 1) is fast and economical for routine control of light to medium fabrics; the trouser method (Part 2) is the general-purpose reference for apparel wovens; the wing method (Part 3) is preferred when the tear direction is unstable; and the tongue double-rip method (Part 4) suits heavy or coated fabrics. For nonwovens and geotextiles, trapezoid-type methods such as GB/T 13763 or ASTM D5587 are typically more appropriate.

Are GB/T 3917 and ISO 13937 results equivalent?

The GB/T 3917:2009 series is a modified adoption of ISO 13937, so the specimen geometry, apparatus principle, and calculation are essentially the same. Results from the two systems generally correlate closely, but because they are formally different standards, certificates for international trade should state exactly which standard was applied, and interlaboratory verification is recommended when switching between them for compliance purposes.

Why do tear results show such high variability on certain fabrics?

Tear propagation is a yarn-by-yarn breakage process, and its variability reflects fabric structure. Loose weaves, ripstop constructions, and fabrics with high yarn mobility can produce very different peak patterns from specimen to specimen. The standards address this by requiring the coefficient of variation to be reported, and laboratories may increase the number of specimens when scatter is high so that the mean is statistically meaningful.

How many specimens are required, and what invalidates a result?

A minimum of five valid specimens per direction is required, taken well away from selvedges and cloth ends. A specimen is invalidated if the tear deviates from the intended path, the specimen slips or is cut by the jaws, the tear fails to complete the specified tearing distance, or the recorded force falls outside the calibrated range of the instrument. All rejections must be documented in the test report.

In what units are tear strength results reported?

Tear force is reported in newtons (N); for very light fabrics tested on the pendulum instrument, millinewtons (mN) may be used. Reports must state the method, the direction of each result, the number of specimens, the mean tear force, and the coefficient of variation, together with any deviations from the standard so that users can judge the reliability of the data.