Dry state breaking strength testing is a fundamental mechanical performance test that measures the maximum tensile force a textile fabric can withstand before rupture when evaluated under standard atmospheric conditions. Governed by internationally recognized standards such as ISO 13934-1, ASTM D5034, and GB/T 3923.1, this test is essential for quality control, product certification, and compliance verification across the apparel, home textile, medical, and technical textile industries. This article explains the testing principles, applicable standards, sample requirements, methods, and practical applications of dry state breaking strength evaluation.
Technical Overview
Dry state breaking strength testing, also referred to as dry tensile strength testing, determines the maximum force that a textile fabric can resist before rupturing when the specimen is tested in a conditioned, non-wetted state. The test is performed on a constant-rate-of-extension (CRE) tensile testing machine, in which a rectangular specimen is clamped between two jaws and extended along its length until breakage occurs. The maximum force recorded at rupture, expressed in newtons (N), together with the elongation at that force, constitutes the primary test result.
The term "dry state" distinguishes this test from wet breaking strength testing, in which specimens are fully immersed in water prior to extension. Because the moisture content of hydrophilic fibers such as cotton, viscose, and wool significantly influences tensile behavior, dry state testing is always conducted on specimens that have been conditioned to moisture equilibrium in a standard atmosphere, as defined in ISO 139 (20 ± 2 °C and 65 ± 4 % relative humidity) or equivalent tropical conditions.
Dry breaking force is one of the most widely specified mechanical durability indicators in national and international product standards for fabrics, including requirements for woven apparel fabrics, bedding, upholstery, medical protective products, and industrial textiles. Manufacturers, buyers, regulatory bodies, and accredited third-party laboratories rely on this test to verify that materials meet contractual and regulatory strength requirements.
Testing Samples
Woven Fabrics
Woven fabrics are the primary application for dry state breaking strength testing. Because woven constructions have clearly defined warp and weft directions, specimens are cut and tested separately in each direction. Typical examples include shirting, trousering, denim, canvas, pocketing fabric, workwear fabric, and lining materials.
Knitted Fabrics
Conventional strip tensile testing is often less suitable for highly elastic knitted structures, which are more commonly evaluated by burst strength methods such as ISO 13938. However, certain low-stretch knits and knitted industrial fabrics can still be assessed by modified strip procedures where the applicable product standard permits.
Nonwoven Fabrics
Nonwoven materials, including medical gown fabrics, interlinings, filtration media, and geosynthetic products, are evaluated for breaking strength using dedicated procedures such as ISO 9073-3. Machine direction and cross machine direction specimens are tested separately due to the pronounced anisotropy of nonwoven structures.
Coated and Laminated Fabrics
Coated, rubberized, and laminated fabrics used in tents, awnings, tarpaulins, protective clothing, and inflatable products are tested using standards such as EN ISO 1421, which addresses tensile strength and elongation of coated fabrics in both dry and wet conditions.
Narrow Fabrics, Webbing, and Straps
Woven narrow fabrics such as seatbelt webbing, harness webbing, lifting sling material, and garment tapes are tested over their full width using strip-type procedures adapted to the product, reflecting their critical load-bearing safety functions.
Testing Items
The principal parameters determined in dry state breaking strength testing include:
- Breaking force (maximum force): the greatest force sustained by the specimen before rupture, expressed in newtons (N).
- Elongation at maximum force: the extension of the specimen, expressed as a percentage of the initial gauge length, at the moment the maximum force is reached.
- Breaking elongation: the extension achieved at the point of complete rupture.
- Force at specified elongation: where required by product specifications, the force recorded at a predefined extension level.
- Statistical evaluation: the arithmetic mean, coefficient of variation, and confidence interval calculated from valid individual results.
Testing Methods
Relevant Standards
The most commonly applied standards for dry state breaking strength testing of fabrics include:
- ISO 13934-1 — Determination of maximum force and elongation at maximum force using the strip method.
- ISO 13934-2 — Determination of maximum force using the grab method.
- ASTM D5034 — Breaking strength and elongation of textile fabrics (grab test).
- ASTM D5035 — Breaking force and elongation of textile fabrics (strip test).
- GB/T 3923.1 and GB/T 3923.2 — Chinese national standards corresponding to the strip and grab methods, harmonized with the ISO series.
- EN ISO 1421 — Tensile strength and elongation of coated fabrics.
- ISO 9073-3 — Breaking strength and elongation of nonwovens.
Specimen Preparation and Conditioning
Specimens are cut representative of the bulk fabric, avoiding selvedge areas, creased or damaged regions, and sample edges. For woven fabrics, specimens are typically taken at least five per direction, with warp and weft specimens staggered so that no two specimens contain the same set of yarns. In the strip method, specimens are cut wider than the required test width and then raveled down to the nominal effective width, typically 50 mm. All specimens are conditioned in the standard atmosphere for textiles until moisture equilibrium is reached, normally a minimum of 24 hours, before tensile testing begins. No water immersion is applied, since the test is performed in the dry state.
Strip Method Procedure
In the strip method, the full width of the specimen is gripped in the jaws of the CRE tensile tester. Under ISO 13934-1 and GB/T 3923.1, a gauge length of 200 mm is normally used, with an extension rate of 20 mm/min for fabrics with elongation below 75 % and 100 mm/min for fabrics with higher elongation. Under ASTM D5035, a shorter gauge length of 75 mm with a speed of 300 mm/min is commonly applied. The specimen is extended to rupture, and the maximum force and elongation are recorded automatically by the testing instrument.
Grab Method Procedure
In the grab method, only the central width portion of a wider specimen is clamped between the jaws, with the front jaws typically gripping a 25 mm central band while the remainder of the fabric width remains unclamped. Under ASTM D5034, specimens of approximately 100 mm by 150 mm are tested using a 75 mm gauge length at a speed of 300 mm/min. The grab method is faster to prepare, better suited to high-strength or coated fabrics where ravelling is impractical, and generally produces results comparable to but not interchangeable with the strip method.
Jaw Breaks and Result Validity
A jaw break occurs when the specimen ruptures within a few millimetres of the jaw line, often caused by jaw damage rather than true fabric strength. When a jaw break produces a result significantly below the mean of the valid results, the specimen is rejected and a replacement is tested. The final reported result is the arithmetic mean of all valid individual results for each test direction, supported by statistical variation data as required by the applicable standard.
Applications
Dry state breaking strength testing serves a wide range of industrial and commercial purposes:
- Apparel quality control: verifying that shirting, denim, workwear, and uniform fabrics meet minimum strength specifications set by buyers and product standards.
- Home textiles: demonstrating compliance of bedding, sheeting, curtain, and upholstery fabrics with strength clauses in European and international product specifications.
- Medical and protective textiles: confirming the mechanical integrity of surgical gowns, drapes, and protective clothing materials referenced in standards such as EN 13795.
- Industrial and technical textiles: qualifying geotextiles, filtration media, coated architectural fabrics, and conveyor and composite substrates for demanding load-bearing applications.
- Automotive and transport interiors: evaluating seat and trim fabrics against OEM and industry durability requirements.
- Trade compliance and certification: providing objective test reports issued by accredited third-party laboratories for export documentation, tender submissions, and regulatory acceptance.
- Research and development: comparing fabric constructions, finishes, and fibre blends during new product development and process optimization.
FAQ
What does "dry state" mean in breaking strength testing?
Dry state means the specimen is tested without any water immersion or wetting treatment, after being conditioned to moisture equilibrium in the standard laboratory atmosphere. This distinguishes the test from wet breaking strength testing, in which specimens are soaked in water before extension. The distinction matters because fibres such as cotton and viscose lose or gain strength significantly when wet.
What is the difference between the strip method and the grab method?
In the strip method, the entire width of the specimen is clamped in the jaws, so all yarns across the test width contribute to the measured force. In the grab method, only a central band of the specimen is gripped, which reduces preparation time and reflects performance in areas of concentrated stress. The two methods yield different numerical results and are not interchangeable; the applicable product standard determines which method must be used.
How many specimens are required for a valid test?
Most standards require a minimum of five valid specimens per test direction, meaning at least five warp and five weft specimens for a woven fabric. Additional specimens are tested if jaw breaks or other invalid failures occur until the required number of valid results is obtained.
Why is conditioning necessary if the test is performed dry?
The moisture content of textile fibres directly affects their tensile behaviour. Conditioning in the standard atmosphere of 20 ± 2 °C and 65 ± 4 % relative humidity ensures that all laboratories test specimens at a reproducible and comparable moisture level, which is essential for consistent, inter-laboratory comparable results.
What happens when a specimen breaks at the jaw edge?
A rupture occurring within approximately 5 mm of the jaw line is classified as a jaw break. If such a result falls well below the mean of the other valid results, it is discarded, a replacement specimen is tested, and the excluded value is documented. This practice prevents jaw-related artifacts from artificially lowering the reported breaking force.
What breaking force values are typically acceptable?
Acceptance levels depend entirely on the product specification and end use. Lightweight apparel fabrics may specify minimum values in the range of roughly 200 N to 350 N, while heavyweight industrial or coated fabrics may require forces exceeding 1000 N. The contractual product standard, buyer specification, or regulatory requirement should always be consulted for the applicable limits.
How long does dry state breaking strength testing take?
Excluding conditioning time of at least 24 hours, the mechanical testing itself is rapid, with each specimen typically rupturing within one to two minutes. A complete test report including sampling, conditioning, testing in both directions, data evaluation, and documentation is generally issued within three to five working days by accredited third-party laboratories.
