Breaking strength testing equipment is a precision instrument used to measure the maximum tensile force that fabrics, yarns, webbings, and other flexible materials can withstand before rupture. As a core quality control tool in textile mills, research laboratories, and accredited third-party testing facilities, it verifies compliance with international standards such as ISO 13934, ASTM D5034, and GB/T 3923. This article explains the working principles, key specifications, applicable sample types, testing methods, and typical applications of breaking strength testing equipment.
Technical Overview
Breaking strength testing equipment, also referred to as a tensile strength tester or universal material testing machine, is engineered to apply a controlled tensile load to a specimen until it fails, recording the maximum force, elongation behavior, and failure characteristics of the material. It is one of the most fundamental instruments in textile and flexible-material quality control, because breaking force and elongation at break directly reflect the durability, structural integrity, and end-use suitability of a product.
Modern instruments operate on the CRE (Constant Rate of Extension) principle, in which the moving clamp travels at a constant, electronically regulated speed while the stationary side measures force through a high-precision load cell. CRE operation is explicitly required by current editions of ISO 13934, ISO 2062, and their ASTM and GB equivalents, replacing the older CRT (Constant Rate of Traverse) pendulum-type machines that are now largely obsolete for standards compliance.
A typical system consists of a rigid load frame (single-column benchtop designs for forces up to approximately 5 kN, dual-column floor-standing frames for higher capacities), a servo motor driving a precision ball screw, interchangeable load cells ranging from 10 N to 50 kN, and a set of specimen grips selected according to the material under test. Force measurement accuracy of class 0.5 or class 1, verified in accordance with ISO 7500-1 and ASTM E4, is standard on laboratory-grade equipment.
- Load frame: single-column or dual-column construction with stiffness sufficient to prevent frame deformation from influencing results
- Drive system: AC servo motor and ball screw providing speed ranges typically from 0.5 to 1000 mm/min with ±1% speed accuracy
- Force measurement: auto-recognized interchangeable load cells covering capacities from 10 N to 50 kN
- Grips and fixtures: pneumatic side-action grips, mechanical wedge grips, capstan yarn grips, webbing fixtures, and custom clamps
- Extension measurement: high-resolution encoder on crosshead displacement, with optional contact or video extensometers for improved elongation accuracy
- Control and software: closed-loop control, real-time force–extension curves, standard-compliant test templates, statistical analysis, and exportable reports
- Safety features: overload protection for the load cell, travel limit switches, and emergency stop
Test parameters such as gauge length, extension rate, pretension, and calculation methods are configured through the software, which then automatically determines maximum force, breaking force, elongation values, and pass/fail verdicts against predefined limits. Results can be archived for traceability and audit purposes in ISO/IEC 17025-accredited laboratory environments.
Testing Samples
Woven and Knitted Fabrics
Apparel fabrics, home textiles, industrial cloth, and technical woven materials are the most common specimens. Testing is performed separately in the warp and weft directions (or course and wale for knits) using strip or grab geometry, in accordance with ISO 13934-1/-2, ASTM D5034/D5035, and GB/T 3923.1/.2. Compliance screening against national textile safety codes such as GB 18401 also relies on minimum breaking force thresholds obtained with this equipment.
Yarns, Sewing Threads, and Elastomeric Fibers
Single-end yarn testing per ISO 2062, ASTM D2256, and GB/T 3916 measures breaking force, elongation, and tenacity expressed in cN/tex. Capstan or pneumatic yarn grips with adjustable pretension prevent slippage and jaw breaks, which is especially critical for fine filament and high-elongation elastomeric yarns.
Webbing, Straps, Tapes, and Braided Materials
Seat belt webbing, lifting slings, lanyards, luggage straps, hook-and-loop tape, and braided cords are tested per ASTM D6775 and related specifications. These high-strength products typically require capacities of 10 kN to 50 kN, wrap-type or pinned grips, and longer gauge lengths to accommodate the large elongations observed before rupture.
Geotextiles and Nonwovens
Nonwoven interlinings, filtration media, medical drapes, and civil-engineering geotextiles are evaluated using wide-width strip methods such as ISO 10319 and ISO 9073-3. Wide specimens (200 mm) may require specialized wide grips or an additional transverse cut mechanism to ensure a controlled rupture within the gauge length.
Coated Fabrics, Laminates, and Technical Textiles
Rubber- or plastic-coated fabrics used in tarpaulins, inflatable structures, protective clothing, and conveyor belting are tested under EN ISO 1421 and ASTM D751. The equipment accommodates the higher forces and lower elongation of these composite constructions by combining robust wedge grips with appropriate speed settings.
Plastic Films and Flexible Sheet Materials
Thin plastic films and flexible barrier materials are assessed using ASTM D882, which uses narrow strips and low-force load cells. This extends the usefulness of a single instrument across both textile and packaging laboratory workloads.
Testing Items
Depending on the selected method and accessories, breaking strength testing equipment can determine the following parameters:
- Breaking force / maximum force: the peak tensile load sustained by the specimen, reported in N or kN
- Breaking elongation and elongation at maximum force: extension at rupture or at peak load, expressed as a percentage of gauge length
- Elongation at specified force: extension measured under a defined preload or reference load
- Tenacity: breaking force normalized by linear density (cN/tex or N/tex), primarily for yarns
- Work of rupture: the energy absorbed up to failure, derived from the area under the force–extension curve
- Initial modulus and yield behavior: indicators of stiffness and elastic response in the low-extension region
- Seam strength and seam slippage: resistance of stitched joints per ISO 13935-1/-2 and ASTM D1683
- Tear and burst resistance: achievable with supplementary fixtures such as trouser-tear grips or diaphragm bursting attachments
- Statistical evaluation: mean, coefficient of variation, and confidence intervals computed across replicate specimens for lot disposition
All results are captured automatically by the software, eliminating manual calculation errors and ensuring consistent reporting across operators and shifts.
Testing Methods
Before testing, specimens must be conditioned in a standard atmosphere in accordance with ISO 139 (20 ± 2 °C and 65 ± 4% relative humidity, or the tropical alternative of 27 ± 2 °C and 65 ± 4% RH) until moisture equilibrium is reached. Representative sampling and proper specimen preparation—cut parallel to yarn directions, free of creases and defects—are prerequisites for valid results.
Strip Method (ISO 13934-1 / ASTM D5035 / GB/T 3923.1)
A rectangular strip, typically raveled to an effective width of 50 mm (or 25 mm for the ASTM ravel strip), is clamped with a gauge length of 200 mm and extended at 20 mm/min per the ISO procedure. If elongation exceeds 75%, the gauge length is reduced to 100 mm with a corresponding speed adjustment. The method measures the strength contribution of the full specimen width and is preferred for precise comparative evaluation of fabric tensile properties.
Grab Method (ISO 13934-2 / ASTM D5034 / GB/T 3923.2)
A 100 mm × 150 mm specimen is gripped in the central area only, with the jaws clamping a 25 mm-wide band across a 50 mm-wide face, leaving lateral edges unsupported. Using a gauge length of 75 mm and a crosshead speed of 300 mm/min, the grab method better reflects the in-service strength of fabrics where local stress concentration occurs, requires less specimen preparation, and is less affected by yarn raveling or slippage.
Single Yarn Method (ISO 2062 / ASTM D2256 / GB/T 3916)
Individual yarn packages are tested using capstan or pneumatic yarn grips with a gauge length of 500 mm and a pretension selected according to linear density. CRE speeds are chosen based on the expected elongation class of the yarn. Output includes breaking force, breaking elongation, and tenacity, with coefficient-of-variation statistics that reveal spinning consistency.
Seam Strength Method (ISO 13935-1/-2)
Specimens containing a sewn seam are tested in strip or grab geometry identical to the base methods, with the seam centered midway between the grips. The seam opening force, seam breaking force, and failure mode (yarn rupture, thread rupture, or fabric tear) are recorded to evaluate stitch type, stitch density, and sewing thread selection.
General Operating Procedure
- Power on the instrument, allow the control system and load cell to warm up, and verify that the machine is within its calibration interval.
- Mount grips appropriate to the specimen, select the standard-compliant test template, and confirm gauge length, speed, and pretension settings.
- Insert the specimen squarely and symmetrically, apply the specified pretension, and clamp both grips securely.
- Start the test; the crosshead extends the specimen at constant rate until rupture occurs.
- Inspect the failure location: results from specimens breaking within the jaw lines (jaw breaks) are rejected and retested unless the standard permits retention.
- Repeat for the required number of replicates (typically five per direction), then review the statistical summary and issue the test report.
Applications
Breaking strength testing equipment serves a broad cross-section of industries wherever the mechanical integrity of flexible materials must be quantified:
- Textile manufacturing: incoming yarn inspection, in-process weaving and knitting control, and finished fabric release testing at mills, dyehouses, and garment factories
- Home and technical textiles: certification of bedding, upholstery, and tarpaulin fabrics against buyer specifications and national safety codes
- Automotive supply chain: verification of seat belt webbing, airbag fabrics, interior trim materials, and safety-critical sewn assemblies
- Personal protective equipment: strength evaluation of harness webbing, straps, and protective garment materials used in fall-arrest and industrial safety products
- Medical textiles: quality control of surgical gowns, drapes, bandages, and single-use nonwoven products
- Geosynthetics and civil engineering: wide-width tensile verification of geotextiles used in road, railway, and landfill construction
- Packaging and films: tensile characterization of plastic films and flexible laminates for converting and sealing performance
- Research and education: materials development, fiber and structure optimization, and academic instruction in textile engineering programs
- Accredited third-party laboratories: compliance testing and certification support for importers, retailers, and regulatory submission
In each setting, the equipment provides objective, repeatable data that supports product development, supplier qualification, claims substantiation, and regulatory compliance.
FAQ
What is the difference between breaking strength and tensile strength?
In textile usage, breaking strength (or breaking force) refers to the maximum tensile force a specimen sustains before rupture, expressed in newtons. Tensile strength, strictly defined, is force divided by the original cross-sectional area (MPa) and is more common for plastics and metals. For fabrics and yarns, standards report breaking force in N and tenacity in cN/tex rather than stress in MPa.
Why do modern standards require CRE-type machines?
CRE (Constant Rate of Extension) instruments extend the specimen at a precisely controlled, uniform rate regardless of the force developed, which improves repeatability and reproducibility between laboratories. Older CRT pendulum machines applied force at a variable rate and produced systematically different results; consequently, ISO, ASTM, and GB test methods now specify CRE equipment for referee testing.
How do I choose the right force capacity?
Select the smallest load cell that still covers your expected maximum force, targeting a working range between roughly 10% and 90% of cell capacity for best accuracy. Typical guidance: apparel fabrics 100 N to 2.5 kN, heavy coated fabrics and webbings 5 kN to 10 kN, and safety webbing or slings 20 kN to 50 kN. Instruments with auto-recognized interchangeable load cells offer the greatest flexibility.
Which grips should be used for different materials?
Pneumatic side-action grips with rubber-coated or fine-serrated faces suit most fabrics; capstan or wrap grips prevent slippage on yarns; wedge grips handle high-force webbing and coated fabrics; and specialized fixtures with wrap radii or pins are used for belts and braided cords. Correct grip selection is the single most effective measure against jaw breaks.
What is a jaw break and how is it handled?
A jaw break occurs when the specimen fails at or inside the clamp line rather than between the grips, usually producing an artificially low result. It is addressed by adjusting clamping pressure, using cushioned jaw liners, re-cutting specimens, or changing grip type. Most standards require discarding jaw-break results and retesting until a valid mid-gauge rupture is obtained.
How often should the equipment be calibrated and verified?
Force indication should be verified at least annually by an accredited calibration service against ISO 7500-1 or ASTM E4, and crosshead speed and displacement should be checked at the same interval. Daily or weekly routine checks with reference specimens or intermediate verification weights, together with documented maintenance, satisfy the equipment-control requirements of ISO/IEC 17025 laboratory quality systems.
Can one machine test fabrics, yarns, and webbing?
Yes. A frame with sufficient capacity, an appropriate set of load cells, and interchangeable grip interfaces can cover the full range from fine yarns to heavy webbing. The software's test templates store the gauge lengths, speeds, and calculations for each standard, allowing rapid changeover between ISO, ASTM, EN, JIS, and GB test methods on a single platform.
