Tensile and Load Testing of Straps and Webbing

Why tensile testing matters

Straps and webbing are used throughout equestrian equipment: girths, billets, breastplates, martingales, reins, headcollars, lead ropes, turnout and travel fittings, barrier straps, protective equipment and stable or yard restraints. They may look simple, but their performance is governed by a chain of interacting components. The webbing itself may be strong while the finished product is weakened by a sharp-edged buckle, an unsuitable fold, poor stitching, heat damage, abrasion, contamination or long-term ultraviolet exposure.

Tensile testing provides controlled evidence about resistance to an applied pulling force. It can answer questions such as:

• What is the maximum force a specified webbing construction withstands before rupture?
• How much does it elongate under load?
• Does a production batch meet a stated minimum?
• Is the finished strap stronger or weaker than the unsewn webbing?
• Has exposure to washing, moisture, abrasion, chemicals or sunlight reduced residual strength?

It does not, by itself, prove that a product is safe in every equestrian application. A laboratory result is specific to the specimen, test arrangement and condition. A straight, unstitched sample of webbing is not equivalent to a complete girth, lead rope or restraint assembly containing hardware and seams.

Essential terminology

Breaking force, breaking strength and ultimate load

Breaking force is the force recorded when the specimen fails under a specified test. It is commonly reported in newtons (N), kilonewtons (kN) or decanewtons (daN). In practical terms, 1 daN is approximately equivalent to the weight-force of 1 kg under standard gravity, although force and mass should not be treated as interchangeable in technical documentation.

Breaking strength is often used in the same general sense, but reports should define the term. Some manufacturers report force per unit width, while others report the result for the complete webbing width. Those values cannot be compared without checking the basis of calculation.

The ultimate load is the greatest force reached during a test. A specimen may continue to carry some force after visible damage begins, or it may fail abruptly. The test report should therefore record the failure mode, not only the peak number.

Elongation

Elongation is the change in length expressed as a percentage of the original gauge length. It may be reported at a specified force, at maximum force or at break. These are different measurements. A webbing can have a high breaking force but substantial extension, or low extension but a less forgiving failure response.

Elongation is affected by fibre type, yarn construction, weave tightness, coatings, moisture, test speed and pre-tension. ASTM D6775 explains that elongation is relevant to the capacity of textile materials to absorb energy and withstand repeated applied forces, but it does not turn elongation into a universal safety rating. ASTM D6775-13(2024) covers breaking strength and elongation of textile webbing, tape and braided material using a split-drum specimen clamp.

Working load, safe working load and minimum breaking load

Minimum breaking load or minimum breaking strength is a failure-related value. It is not a recommended operating load.

Working load limit and safe working load are application limits established by the manufacturer or by the relevant regulatory or engineering framework. They should account for foreseeable loading, configuration, ageing, manufacturing variation and an appropriate safety factor. A safety factor is not a property of the fibre alone: it belongs to the defined product, use and risk assessment.

For work equipment used to lift loads, GB businesses must distinguish ordinary tack from equipment that falls within lifting-equipment duties. HSE guidance states that lifting equipment and accessories must be of adequate strength and clearly marked with their safe working load where applicable. Lifting accessories such as web slings are subject to specific examination requirements under LOLER. That does not mean that an ordinary lead rope, headcollar or riding strap automatically becomes a LOLER lifting accessory; classification depends on the actual use. HSE LOLER guidance and the HSE guidance on thorough examination should be consulted for workplace lifting applications.

What is being tested?

Webbing material

A material test examines the woven, knitted or otherwise constructed textile before it is made into a product. Important variables include:

• fibre polymer, such as polyester, polyamide or polypropylene;
• filament or staple-yarn construction;
• webbing width and thickness;
• warp and weft density;
• coatings, finishes and edge treatments;
• colour and pigment system;
• batch, supplier and production date.

ISO 13934-1 specifies a strip method for determining maximum force and elongation at maximum force in textile fabrics. It is mainly applicable to woven fabrics, including fabrics with stretch introduced by elastomeric fibres, mechanical treatment or chemical treatment. It is not normally intended for every type of coated, nonwoven or specialist fabric. ISO 13934-1:2013 remains a current ISO publication following review and confirmation in 2024.

For narrow webbing, ASTM D6775 is often more directly relevant than a general fabric strip method because it addresses textile webbing, tape and braided material. The standard specifies a split-drum clamp arrangement, which helps reduce damage caused by gripping a narrow, flexible specimen in ordinary flat jaws.

Finished strap or assembly

A finished-assembly test includes the features that exist in service: stitching, folds, holes, adjustment points, buckles, rings, hooks, snaps, bonded sections, rivets and protective sleeves. This is usually more informative for product qualification because the weakest component may not be the webbing.

Testing should identify whether failure occurred in:

• the webbing away from the fittings;
• the folded or stitched termination;
• the thread or stitch pattern;
• the buckle, ring, hook or snap;
• the webbing where it bears against hardware;
• a hole, cut edge or punched opening;
• a bonded, welded or heat-sealed section.

A result that merely says “failed at 8 kN” is incomplete. A useful report states the specimen description, dimensions, conditioning, test method, equipment, loading rate, number of replicates, individual results, mean, minimum, variation and failure location.

How a tensile test is performed

Sampling and conditioning

Representative sampling is a quality-assurance issue, not an administrative detail. Samples should be linked to a defined production lot and should include material from different rolls, machines or production periods where variation is plausible. Taking only the easiest or best-looking sample can conceal process drift.

Textiles may be conditioned before testing at a specified temperature and relative humidity. Moisture can affect dimensions, friction, flexibility and strength, particularly in hygroscopic fibres. If the product will be used wet, muddy, washed or outdoors, dry laboratory conditioning alone may not represent service conditions.

Clamping and alignment

The machine applies force through grips or drums while measuring force and extension. The specimen must be aligned so that the load is centred and the webbing is not twisted. Misalignment can introduce bending, edge loading or premature damage.

Ordinary flat jaws can crush or cut narrow webbing. Split-drum or capstan-style arrangements distribute the load more gradually. However, a clamp can also mask a material weakness if the specimen slips or fails at an artificial point. A laboratory should record whether the failure was a valid gauge-length break or a grip-related failure.

Loading rate and measurement

Textile tensile methods specify or control the rate at which the grips separate. Changing the rate may change the measured peak force and elongation because polymers and textile structures are rate-sensitive. Tests from two laboratories should not be compared casually if they use different methods, gauge lengths, grip geometries or rates.

Testing machines should be suitable for the force range, correctly aligned and calibrated. ASTM D6775 specifically warns that comparisons between laboratories require caution where precision information is incomplete and recommends comparative testing when results differ materially. That is an important reminder that a single high number is not automatically more reliable than a lower number from a different method.

Why webbing construction matters

Polyester

Polyester is widely used where low stretch, good abrasion performance and outdoor durability are required. Technical information from Teufelberger describes polyester as having good breaking loads, low stretch, chemical and UV resistance, salt-water resistance and good abrasion performance in wet and dry conditions. These are useful general material characteristics, not a guarantee for every polyester webbing construction. Teufelberger raw-material information also notes that performance depends on the fibre and application.

Polyamide or nylon

Polyamide can provide high strength, flexibility and useful energy absorption, but it absorbs more moisture than polyester and may behave differently when wet. Its resistance to sunlight is generally less favourable than polyester’s. Teufelberger reports that polyamide can absorb water and has lower UV resistance than polyester in its comparative rope-material information.

For equestrian use, the practical conclusion is not that nylon is unsuitable. It is that the choice should reflect the desired handling, stretch, wet performance, abrasion environment and expected sunlight exposure. A nylon strap may feel supple and comfortable, while a polyester strap may provide more dimensional stability and outdoor resistance.

Polypropylene and specialist fibres

Polypropylene is light and has no significant water absorption, but its strength, heat behaviour and abrasion performance must be evaluated for the specific construction. High-modulus polyethylene, aramid and other specialist fibres can provide very high strength or low extension, but may have limitations involving creep, UV, heat, bending or abrasion. A stronger fibre is not automatically a better choice if the product cannot tolerate the way it is folded, stitched or handled.

Webbing strength is not assembly strength

The finished assembly is frequently governed by stress concentrations. A buckle bar bends the webbing around a small radius. A ring may force the strap to bear against a narrow contact area. A punched hole removes material. A keeper or folded return can create multiple layers with unequal load sharing. Stitching creates perforations and transfers force through thread rather than through continuous webbing.

Stitch design therefore matters. Relevant variables include stitch type, thread material, thread size, stitch density, seam length, edge distance, back-tacking, bartack geometry and whether the seam is loaded in peel, shear or direct tension. More stitches do not automatically mean greater strength: excessive needle perforation, poor thread tension or an unsuitable seam can weaken the textile.

Hardware must be tested as part of the system. A buckle can deform or release before the webbing breaks. A snap may open under side loading even though its nominal tensile rating is high. Corrosion, casting defects, sharp edges and poor heat treatment can create failure modes not visible in a simple webbing test.

For product development, the best programme normally includes separate tests for raw webbing, stitched terminations, hardware attachment and complete assemblies. The acceptance criterion should be based on the intended use and failure consequences, not merely on the highest achievable laboratory load.

Static, cyclic and environmental testing

Static tensile testing

A static pull measures the response to a steadily increasing load. It is useful for ranking materials, checking batch consistency and verifying a minimum breaking requirement. It does not reproduce every service event, particularly repeated pulls, sudden stops, rubbing or shock loading.

Cyclic and fatigue testing

Cyclic loading applies and releases a defined force repeatedly. It can reveal stitch slippage, permanent extension, yarn migration, coating damage and progressive weakening. The useful test question is not simply “how many cycles?” but “how many cycles at what load, extension, rate, bend radius and environmental condition?”

A strap used for repeated leading, restraint or adjustment may experience thousands of lower-load cycles rather than one maximum pull. A product that survives a single overload test may nevertheless deteriorate in normal service through abrasion or repeated flexing.

Abrasion

Abrasion can reduce strength before the webbing looks dramatically damaged. It may occur against buckles, rings, trailer fittings, stable hardware, rough timber, concrete or another strap. ASTM lists specific textile abrasion methods, including D6770 for textile webbing using a hex-bar method. Such methods are useful only when the laboratory exposure resembles the service mechanism.

UV, moisture, chemicals and heat

Outdoor tack and yard equipment can experience sunlight, wetting and drying, mud, sweat, detergents, disinfectants, oils and temperature changes. UV exposure may reduce residual strength and alter stiffness or surface appearance. Teufelberger’s published UV discussion warns that visual inspection alone cannot reliably establish residual rope strength and reports greater breaking-load reduction in the tested polyamide ropes than in the tested polyester ropes. The finding is relevant as a caution about material choice and inspection, but it should not be treated as a universal numerical prediction for every webbing product. Teufelberger UV-resistance information.

Accelerated ageing can help compare constructions, but it is not identical to real weathering. The exposure spectrum, temperature, humidity, tension and duration must be stated. A claim such as “UV resistant” is weak unless it identifies the test basis, acceptance criterion and residual-strength requirement.

Interpreting test results responsibly

When reviewing a certificate or supplier report, check:

• the exact material and product reference;
• webbing width, thickness and construction;
• the test standard and edition;
• specimen conditioning and moisture state;
• test speed, gauge length and grip arrangement;
• number of specimens and individual results;
• mean, minimum and spread of results;
• where each specimen failed;
• whether the sample was raw webbing or a finished assembly;
• laboratory identity, equipment status and report date;
• any deviations from the stated method.

Do not compare a manufacturer’s advertised “breaking load” with a laboratory’s “minimum breaking force” unless the test basis is equivalent. Do not divide a breaking-load figure by an assumed safety factor and present the result as an approved working load unless the manufacturer has established that rating for the actual product and configuration.

Results should also be considered statistically. A batch with a high average but one very low result may present a process-control problem. A small number of specimens can indicate a problem but may not characterise production variability. For safety-critical products, sampling plans, traceability and defined rejection criteria are as important as the test machine.

Inspection and quality assurance in equestrian businesses

Users should inspect straps before use and after events likely to cause damage. Look for cuts, edge fraying, pulled or broken stitches, glazing, melted fibres, severe fuzzing, distortion, chemical staining, stiff or brittle sections, colour change, corrosion, deformed hardware and damage concentrated around holes or buckles.

Visual inspection has limitations. A strap may retain an acceptable appearance while having reduced residual strength, particularly after UV exposure, chemical contact or internal abrasion. Conversely, surface fuzzing does not automatically quantify the remaining strength. Where failure could injure a person or horse, uncertainty should favour removal from service and replacement rather than improvised load testing.

Businesses that manufacture or sell equipment should maintain supplier specifications, incoming inspection records, batch identification, approved patterns, thread and hardware specifications, seam samples, test reports, complaints and corrective actions. Any change in webbing supplier, fibre, dye, coating, width, stitching machine, thread or hardware should trigger a review and, where appropriate, comparative testing.

For lifting equipment used at work, informal “pull tests” are not a substitute for the examination and marking regime required by LOLER. HSE states that routine overload testing can itself damage some lifting equipment and that the need and nature of testing should be determined through risk assessment, manufacturer information and competent-person judgement. HSE thorough-examination guidance.

Common misconceptions

• “The webbing is rated at 1,000 kg, so the finished strap is rated at 1,000 kg.” Not necessarily. Seams, hardware, bend radii and configuration can reduce the assembly capacity.
• “A thicker strap is always stronger.” Thickness may improve resistance to wear, but strength also depends on yarn, weave, width, finishing and terminations.
• “If it looks sound, it is sound.” Appearance cannot quantify all UV, chemical, fatigue or internal damage.
• “A higher breaking load means a safer product.” Only if the complete design, handling, compatibility, failure mode and working-load limit are appropriate.
• “A proof load is the same as a breaking test.” A proof test demonstrates survival at a specified load; a breaking test determines failure behaviour. They serve different purposes.
• “Any tensile machine can test webbing.” Grip geometry, alignment, calibration and loading rate can materially affect the result.

Practical specification checklist

For a new or revised strap product, a concise technical specification should define:

1. intended use and foreseeable loading;
2. webbing fibre, width, thickness, colour and construction;
3. hardware material, dimensions and corrosion expectations;
4. stitch pattern, thread and termination geometry;
5. minimum assembly breaking force, if appropriate;
6. working-load limit or other user-facing limitation;
7. test method, conditioning, loading rate and sample number;
8. environmental tests and residual-strength criteria;
9. inspection, care, replacement and traceability requirements.

The strongest evidence is not one impressive test result. It is a coherent link between design intent, controlled manufacture, representative testing, realistic environmental exposure, clear user limitations and a documented inspection system.

Related industry reference: For businesses moving from technical research into trade sourcing, explore equestrian suppliers and manufacturers on EquiGuild.

Sources and further reading

• ISO 13934-1:2013 — Textiles: tensile properties of fabrics, strip method.
• ASTM D6775-13(2024) — Breaking strength and elongation of textile webbing, tape and braided material.
• ASTM D5035-11(2024) — Breaking force and elongation of textile fabrics, strip method.
• BS EN 12195-2 — Load restraint assemblies: web lashing made from man-made fibres.
• Health and Safety Executive — LOLER overview.
• Health and Safety Executive — Thorough examinations and inspections of lifting equipment.
• Teufelberger — Raw materials for fibre ropes: performance characteristics.
• Teufelberger — UV exposure and residual rope strength.

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