Breaking Strength Testing: International Standards, Methods, and Applications Explained

Breaking strength testing is a fundamental mechanical evaluation used to determine the maximum tensile force a material can withstand before rupture, making it essential for quality control across the textile, geotextile, and industrial fabric industries. This technical guide explains the major international standards for breaking strength testing—including ISO, ASTM, EN, GB, and JIS frameworks—covering applicable sample types, test parameters, methodologies, and practical applications. Whether you are a manufacturer, supplier, or quality engineer, understanding these standards ensures accurate, comparable, and globally accepted test results from accredited third-party laboratories.

Technical Overview

Breaking strength, also referred to as tensile strength or breaking force, is defined as the maximum force a specimen sustains during a tensile test carried out to rupture, expressed in newtons (N). It is one of the most widely performed mechanical tests for flexible materials and serves as a primary indicator of product durability, process consistency, and fitness for purpose.

Because test results must be comparable between suppliers, buyers, and regulators in different countries, breaking strength testing is governed by a family of internationally recognized standards developed by leading standards organizations:

• ISO (International Organization for Standardization) – ISO 13934-1 (strip method) and ISO 13934-2 (grab method) for fabrics; ISO 13935-1/-2 for seam tensile properties; ISO 1421 for coated fabrics; ISO 9073-3 for nonwovens; ISO 2062 for yarns; ISO 10319 for wide-width geotextiles.
• ASTM International – ASTM D5034 (grab method) and ASTM D5035 (strip method) for textile fabrics; ASTM D1683 for seam strength; ASTM D2256 for yarn tensile properties; ASTM D6775 for webbing and braided narrow fabrics.
• EN (European Norms) – EN ISO 13934-1 and EN ISO 13934-2, which are European adoptions of the corresponding ISO methods.
• GB (Chinese National Standards) – GB/T 3923.1 and GB/T 3923.2, which are technically aligned with ISO 13934-1 and ISO 13934-2 respectively.
• JIS (Japanese Industrial Standards) – JIS L 1096, which specifies strip and grab tensile methods for woven and knitted fabrics.

All of these methods are performed on constant-rate-of-extension (CRE) universal tensile testing machines equipped with appropriate clamps, load cells, and software for recording force-extension curves. Selecting the correct standard depends on the material type, product specification, contractual requirements, and target market.

Testing Samples

Breaking strength testing applies to a broad range of flexible materials. The principal sample categories and their corresponding standards are summarized below.

Woven Fabrics

Woven fabrics for apparel, home textiles, and industrial applications are typically tested in the warp and weft directions using ISO 13934-1, ISO 13934-2, ASTM D5035, ASTM D5034, or GB/T 3923.1/.2. Specimens are cut parallel to the yarn directions so that the applied load acts along the yarn axis.

Knitted Fabrics

Knitted fabrics are tested in the course and wale directions. Because knits exhibit high elongation, a higher extension rate and, in some cases, modified specimen preparation are applied in accordance with ISO 13934-1 or ASTM D5035.

Nonwoven Fabrics

Nonwoven materials used in filtration, hygiene, medical, and interlining products are evaluated under ISO 9073-3 (strip method) or the corresponding grab procedures, with specimens cut in both the machine and cross-machine directions.

Coated and Laminated Fabrics

Rubber- or plastics-coated fabrics used for tarpaulins, awnings, inflatable structures, and protective clothing are tested under ISO 1421, which specifies strip and grab procedures for coated textiles.

Yarns, Threads, and Sewing Threads

Single-end yarns are tested under ISO 2062 or ASTM D2256 to determine breaking force, elongation, and tenacity (cN/tex), which are critical inputs for spinning, weaving, and sewing performance.

Webbings, Straps, and Narrow Fabrics

Narrow fabrics such as seatbelt webbing, lifting slings, lanyards, and straps are evaluated under ASTM D6775 or related product-specific requirements, usually in the full finished width.

Geotextiles and Industrial Textiles

Geosynthetics for road, railway, and civil engineering applications are tested by the wide-width tensile method of ISO 10319, which uses wide specimens (typically 200 mm) to better represent field loading conditions.

Ropes and Cords

Ropes and cords are tested under ISO 2307, which specifies specimen length, pretension, and termination requirements appropriate to braided, twisted, and plaited rope constructions.

Testing Items

A breaking strength test program typically reports the following parameters:

• Breaking force (maximum force) – the peak force recorded before rupture, expressed in newtons (N); results are reported as individual values and the mean for each direction.
• Elongation at maximum force – the extension of the specimen, expressed as a percentage of the original gauge length, at the moment peak force is reached.
• Elongation at break – the extension at the point of rupture, where applicable.
• Breaking tenacity – the breaking force normalized by linear density, expressed in cN/tex or N/tex, mainly for yarns.
• Seam breaking strength – the force required to break a seamed specimen, determined under ISO 13935-1 (strip) or ISO 13935-2 (grab) and ASTM D1683.
• Seam slippage resistance – the resistance of yarns at a seam to slippage, measured under the ISO 13936 series (fixed load, fixed seam opening, or progressive force methods).
• Statistical data – coefficient of variation (CV) and, where required, the 95% confidence interval of the mean, together with identification of jaw breaks.

Unit conversions are frequently required in international trade: 1 kgf = 9.807 N and 1 lbf = 4.448 N.

Testing Methods

Strip Method (ISO 13934-1 / ASTM D5035 / GB/T 3923.1)

In the strip method, a rectangular specimen of 50 mm effective width is cut or raveled from the fabric and gripped across its full width. Under ISO 13934-1, the gauge length is 200 mm with a rate of extension of 20 mm/min for fabrics with elongation at or below 75%; for higher-elongation fabrics, a 100 mm gauge and 100 mm/min rate are used. The pretension is selected according to fabric mass per unit area (typically 2 N, 5 N, or 10 N). ASTM D5035 commonly uses a 25 mm or 50 mm strip width with a nominal 75 mm gauge length and a crosshead speed of 300 mm/min. The strip method reflects the intrinsic strength of the yarns and fabric construction.

Grab Method (ISO 13934-2 / ASTM D5034 / GB/T 3923.2)

In the grab method, a wider specimen (typically 100 mm wide) is gripped only in its central area by jaw faces of 25 mm width, so that the load is concentrated in a narrow zone. ISO 13934-2 specifies a gauge length of 100 mm and a rate of extension of 50 mm/min, while ASTM D5034 uses a 75 mm gauge length and 300 mm/min. The grab method is faster, more practical for hard-to-ravel fabrics, and better represents the strength of a fabric when stressed at a localized point, such as a seam or clamp attachment.

Seam Strength Testing

Seamed specimens are prepared using production seam settings and tested in the same strip or grab configuration described above, following ISO 13935-1, ISO 13935-2, or ASTM D1683. The reported seam breaking strength, together with a description of the failure mode (fabric rupture, thread breakage, or yarn slippage), is essential for garment and technical product durability assessment.

Yarn Tensile Testing

Single yarns are tested on CRE machines under ISO 2062 or ASTM D2256, typically using a 500 mm or 250 mm gauge length respectively, with extension rates selected according to the expected elongation at break. Results include breaking force, breaking tenacity, elongation at break, and initial modulus where required.

Conditioning and Test Atmosphere

Prior to testing, specimens are conditioned in the standard atmosphere specified in ISO 139: 20 ± 2 °C and 65 ± 4 % relative humidity (or the alternative tropical atmosphere of 27 ± 2 °C and 65 ± 4 % RH) until moisture equilibrium is reached, normally a minimum of 24 hours. Conditioning is mandatory because moisture content significantly influences the tensile behavior of hygroscopic fibers such as cotton, viscose, and wool.

Specimen Preparation and Valid Results

• At least five valid specimens are tested in each principal direction (warp/weft or course/wale), with specimens located no closer than 150 mm from the fabric selvedge and arranged so that no two contain the same lengthwise yarns.
• Results from specimens that break within 5 mm of the jaw line and yield values markedly below the mean are discarded and replacement specimens are tested; such events are noted as jaw breaks.
• Slippage, jaw breaks, and invalid ruptures must be recorded in the test report, together with the standard used, machine parameters, and specimen details.

Applications

Breaking strength testing against international standards supports a wide range of industries and regulatory contexts:

• Apparel and home textiles – verifying fabric and seam durability for shirts, workwear, upholstery, bedding, and curtains against buyer specifications.
• Personal protective equipment (PPE) – demonstrating the mechanical integrity of fall-arrest webbing, harnesses, gloves, and protective clothing required under EN product standards.
• Automotive and transportation – qualification of seat fabrics, airbag materials, seatbelt webbing, and interior trim components.
• Medical textiles – quality control of gowns, drapes, bandages, and single-use nonwoven products.
• Geotextiles and civil engineering – wide-width tensile verification of geosynthetics used in roads, embankments, and drainage systems under ISO 10319.
• Industrial and coated fabrics – certification of tarpaulins, tents, sails, conveyor covers, membrane structures, and filtration media.
• Packaging and lifting products – validation of straps, slings, sacks, and flexible intermediate bulk containers (FIBC).
• Trade compliance and certification – providing comparable test evidence for customs, product certification schemes, contractual acceptance, and dispute resolution, typically issued by accredited third-party laboratories.

FAQ

What is the difference between the strip method and the grab method?

The strip method grips the full width of a narrow specimen (typically 50 mm) and measures the intrinsic strength of the yarns and fabric structure. The grab method grips only the central portion of a wider specimen with narrow jaws (25 mm), simulating localized stress. ISO 13934-1/ASTM D5035 cover the strip method, while ISO 13934-2/ASTM D5034 cover the grab method; results from the two methods are not directly comparable.

Which standard should I choose: ISO, ASTM, EN, or GB?

The choice depends on the destination market and contractual requirements. European buyers commonly reference EN ISO 13934-1/-2, North American buyers typically specify ASTM D5034 or D5035, and Chinese national requirements align with GB/T 3923.1/.2. Because gauge lengths, speeds, and specimen dimensions differ between standards, the specific method must always be stated in test reports and purchase agreements.

How many specimens are required for a valid test?

ISO and ASTM methods generally require a minimum of five valid specimens per direction (warp and weft, or course and wale). Specimens that slip in the jaws or break at the jaw line with abnormally low values are discarded and replaced.

Why is conditioning necessary before testing?

Most textile fibers are moisture-sensitive, and their tensile properties change with humidity and temperature. Conditioning in the standard atmosphere defined by ISO 139 (20 ± 2 °C, 65 ± 4 % RH) ensures reproducible and comparable results between laboratories.

How are breaking strength results evaluated for acceptance?

There is no universal pass/fail threshold; acceptance criteria are defined by product specifications, buyer contracts, or product safety standards for each end use. The test report should state the mean breaking force, elongation values, the standard applied, and any deviations so that results can be judged against the agreed limits.

Can breaking strength testing be outsourced?

Yes. Manufacturers and traders routinely commission testing from accredited third-party laboratories that operate ISO/IEC 17025-accredited facilities and hold the full set of ISO, ASTM, EN, GB, and JIS testing capabilities, providing internationally recognized test reports for compliance and commercial purposes.