Cyclic Fatigue Testing for Equestrian Straps, Buckles and Attachment Points

Why cyclic fatigue testing matters

A strap assembly can pass a one-off tensile test and still be unsuitable for equestrian use. Repeated tightening, flexing, loading, unloading, rubbing over hardware, contamination, ultraviolet exposure and temperature changes can progressively reduce its margin of safety. Cyclic fatigue testing is intended to expose that progressive deterioration before it appears in service.

The relevant object is usually not the webbing or leather in isolation. It is the complete load path: strap material, folds, stitch pattern, rivets or screws, buckle, D-ring or other attachment hardware, keeper loops, reinforcement patches and the structure to which the assembly is fixed. In a girth, for example, the critical location may be the buckle fold, the stitching around the billet, the interface between elastic and non-elastic sections, or the saddle attachment rather than the visibly strongest part of the strap.

For equestrian products, cyclic testing is especially important because loading is variable and movement-dependent. A breastplate, martingale, headcollar, lead rope, girth, breastcollar, safety stirrup or body-protector closure may experience thousands of small load changes interspersed with occasional high loads. The direction of force can also change as the horse moves, rolls, jumps, pulls back or becomes entangled.

Fatigue testing does not predict an exact service life by itself. It is a controlled comparison or qualification tool. Its value depends on whether the test reproduces the important features of use, whether failure criteria were defined in advance, and whether the test results are linked to production controls and field evidence.

Key terms

Fatigue is not the same as abrasion or static strength

These tests answer different questions.

• Static tensile testing asks how much force a new specimen can withstand when loaded once, usually to rupture.
• Cyclic fatigue testing asks how the assembly changes under repeated loading and whether it survives a defined number of cycles.
• Abrasion testing measures resistance to rubbing under specified conditions. ASTM D6770, for example, expresses textile-webbing abrasion performance as retained breaking strength, but explicitly warns that laboratory abrasion results do not automatically predict actual wear life in a particular end use. ASTM D6770-21
• Environmental conditioning examines the effect of water, sweat, detergents, mud, salt, heat, cold, ultraviolet exposure or chemicals.
• Dimensional and functional testing checks whether a buckle still adjusts, locks, releases and retains the strap as intended.

A robust assurance programme normally combines these approaches. A strap may retain much of its tensile strength while becoming difficult to adjust, developing sharp broken fibres, losing stitch security or slipping through a buckle. Conversely, a component may show cosmetic wear without a material reduction in strength. The test plan must therefore record both strength and function.

What makes an equestrian fatigue test representative?

Define the load path

Before selecting a test machine, map the force route through the product. Identify where force enters, where it changes direction and where it leaves the assembly. Include all intended folds, holes, keeper loops, adjustment sections, sewn joints, bonded areas and hardware. The specimen should be built using the production materials, production machinery and normal tolerances. Testing a perfect laboratory splice or an unrepresentative straight length of webbing can conceal the weakness of the finished product.

Where an attachment point is fixed to a saddle, body protector, air-jacket harness or other substrate, the substrate should be included if it can deform or fail. A strong D-ring attached to weak fabric is not a strong attachment point. The test fixture should reproduce the support, curvature and load angle found in service, or the deviation should be clearly documented.

Choose a realistic loading profile

Many basic fatigue tests use a sinusoidal or triangular load wave between fixed minimum and maximum forces. This is useful for repeatability, but real equestrian loading is rarely a perfect waveform. A lead rope may experience low-level repeated tension punctuated by sharp pulls; a girth may experience a changing load as the horse moves; a body-protector closure may be loaded during impact and then unloaded rapidly.

For development work, a stepped programme can be more informative than one arbitrary cycle count. For example, specimens may undergo a conditioning phase at a representative service load, an elevated-load phase intended to model foreseeable severe use, and then residual-strength testing. The levels and cycle counts must be justified by product risk analysis. They should not be presented as universal values for all equestrian equipment.

Frequency also matters. High cycling frequencies can generate heat, alter polymer behaviour and prevent moisture or contamination from acting as it would in use. Low frequencies may better represent intermittent loading but increase test duration. The chosen frequency should be reported, monitored and kept low enough that it does not introduce an artificial failure mechanism unless accelerated testing has been validated.

Control displacement as well as force

Force-controlled testing is appropriate where the service demand is best described by tension. Displacement-controlled testing can be useful where the product is repeatedly stretched through a known movement or where a machine must prevent sudden load loss. The test report should state which variable was controlled, the permitted tolerance, the waveform, the load ratio, the cycle rate and the measurement method.

Test more than one specimen

Textile and sewn products naturally vary with yarn placement, stitch formation, edge finishing and operator or machine settings. Hardware can vary with casting, forging, stamping, plating, heat treatment and surface finish. A single specimen can demonstrate a failure, but it cannot establish reliable production performance. A meaningful programme normally uses multiple specimens from relevant production lots, with samples selected to represent material and manufacturing variation.

When comparing two designs, change one material or construction feature at a time where practical. Record whether results are being used for design screening, supplier acceptance, process validation, conformity assessment or investigation of a field failure. Those purposes require different sampling and statistical approaches.

Testing the strap, buckle and attachment together

Webbing and leather

Webbing performance depends on fibre type, yarn construction, weave, width, thickness, coatings, edge treatment and stitching. Nylon, polyester and polypropylene do not respond identically to moisture, ultraviolet exposure, creep, heat or abrasion. Leather adds further variables: species, fibre structure, tanning, thickness, grain direction, moisture condition, edge finishing and hole placement.

Testing a straight webbing strip is useful for material comparison, but it does not reproduce bending around a buckle bar or D-ring. A representative specimen should include the tightest bend radius and the normal contact pressure. If the product uses a folded end, test the fold. If it uses box-X stitching, bartacks, zig-zag stitching or rivets, test the actual joint.

Buckles and adjusters

A buckle can fail through fracture, deformation, tongue or bar bending, accidental release, strap slippage, sharp-edge formation or loss of adjustment. Cyclic loading should therefore be combined with repeated adjustment and, where relevant, buckle-abrasion conditioning.

The strap must be threaded in the normal configuration. Testing a buckle with a straight pull through an arrangement that does not match use can produce misleading results. Hardware geometry matters: a small radius or burr can concentrate stress and cut fibres during each cycle. The condition of the strap after cycling should be examined under suitable magnification, not only by looking for complete breakage.

For rider-safety products, closure security is a distinct issue from webbing strength. EN 13158:2018 covers protective jackets, body protectors and shoulder protectors for equestrian use and includes requirements relating to restraint, adjustability, ergonomics, construction and impact performance. It is not a general fatigue standard for every equestrian strap, nor does compliance with it automatically qualify unrelated tack components. EN 13158:2018 scope summary

Stitching, rivets and sewn-on hardware

In stitched assemblies, fatigue may begin with thread breakage, progressive seam opening, needle damage, fabric tearing or localised distortion around the first and last stitches. The stitch count alone is not a sufficient quality indicator. Thread size, thread material, tension, stitch balance, back-tacking, edge distance, seam design and the interaction between layers all matter.

Rivets and screws can introduce hole-edge stress, local crushing or fretting. A riveted attachment should be inspected for loosening, rotation, mushrooming, cracking and tearing of the surrounding material. If a backing washer or reinforcement patch is part of the production design, omitting it from the specimen invalidates the comparison.

Environmental and preconditioning stages

Equestrian equipment is exposed to an unusually mixed environment: sweat, rain, stable disinfectants, mud, urine, dust, tack-cleaning products, salt, heat in transport vehicles and cold storage. No single environmental sequence represents every yard or discipline. The manufacturer should identify the credible exposures for the product and explain the chosen conditioning.

Conditioning may be carried out before cycling, during cycling, or in repeated blocks. A wet strap can behave differently from a dry strap; a polymer can soften or stiffen with temperature; leather can swell, dry and crack; corrosion can change hardware geometry or produce rough edges. If ultraviolet exposure is relevant, it should be treated as a separate controlled variable rather than assumed to be represented by general ageing.

Environmental tests should be followed by functional inspection and, where appropriate, residual-strength testing. A pass after dry cycling does not cancel a failure after wet or contaminated cycling. Results should identify the exact sequence, exposure duration, temperature, humidity, fluid concentration and recovery time.

Coated fabrics and laminated constructions require particular care. Coating adhesion is a separate property from tensile strength; ISO 2411:2024 specifies a method for determining the adhesion strength of rubber- or plastics-coated fabrics. It may be relevant to coated protective products, but it does not by itself establish the fatigue life of a finished strap assembly. ISO 2411:2024

Failure modes and what they reveal

Failure location is as important as cycle count. A specimen that breaks in the machine grip may indicate a fixture problem rather than a product failure. A specimen that breaks within a specified distance of the grip may need to be repeated if the grip has introduced stress concentration. Test laboratories should define invalid tests before testing begins.

Interpreting results responsibly

A statement such as “passed 100,000 cycles” is incomplete without the load range, specimen design, environment, frequency, acceptance criteria and number of samples. It does not mean the product is safe for any load or any period. Nor does it establish that a different width, colour, stitch pattern, buckle, size or supplier version will perform identically.

Useful acceptance criteria may include:

• no complete separation of the load path;
• no accidental release or loss of intended adjustment;
• no crack, sharp edge or deformation that creates a new hazard;
• no strap slippage above a defined limit;
• minimum retained breaking strength after conditioning;
• specified limits for seam opening, elongation or permanent deformation; and
• successful operation by a defined method after testing.

Criteria should be set before looking at the results. Otherwise, there is a risk of treating an unexpected failure as acceptable simply because the product survived many cycles. Equally, a cosmetic change should not automatically be classified as a safety failure unless it affects function or indicates deeper damage.

For production quality assurance, fatigue testing is usually supported by simpler controls: incoming-material identification, width and thickness checks, hardware dimensional inspection, stitch-pattern verification, pull testing of representative assemblies, traceability and documented change control. Requalification is prudent when a supplier, fibre, leather source, coating, buckle design, thread, sewing machine setting or attachment method changes.

What purchasers and trade professionals should ask

Retailers, fitters, riding schools and manufacturers should be cautious with unsupported claims such as “heavy duty”, “tested to destruction”, “military grade” or “will last a lifetime”. These phrases do not state what was tested or under which conditions.

More useful questions include:

1. Was the finished assembly tested, or only the raw webbing or buckle?
2. What load range, cycle count, frequency and environmental conditions were used?
3. How many specimens were tested and were they from production stock?
4. What constituted failure: breakage, slippage, accidental release, deformation or loss of function?
5. Was residual strength measured after cycling?
6. Does the test cover the exact size, hardware, stitching and attachment configuration being sold?
7. What inspection and replacement guidance is supplied to the user?
8. Is the claim linked to a recognised product standard, a laboratory report, an internal specification or only a marketing statement?

For products that are personal protective equipment, GB suppliers must consider the applicable product legislation and conformity obligations. The HSE explains that Regulation (EU) 2016/425, as incorporated into GB law, sets essential health and safety requirements for PPE, while OPSS provides guidance for manufacturers, importers and distributors. Product classification should not be assumed merely because an item is used around horses. HSE: Using PPE—product safety and supply and OPSS: PPE Enforcement Regulations 2018

For ordinary tack and leisure products outside a specific regime, the general product-safety duties still matter. OPSS states that businesses making, importing, distributing or selling consumer products in the UK are responsible for ensuring that products are safe in normal and reasonably foreseeable use. OPSS: Product safety advice for businesses

Common misconceptions

“The webbing has a high breaking load, so the product is safe.”

Breaking load is only one property of one component, often measured on a straight specimen. The weakest component, the load angle and the joint construction govern the finished assembly.

“A static pull test is equivalent to fatigue testing.”

It is not. Static testing may identify gross under-strength, while fatigue testing can reveal progressive damage, slippage and loss of function at loads well below the new-product breaking load.

“More cycles always means a better test.”

Only if the load, frequency, environment and failure criteria remain relevant. An enormous cycle count at an unrealistic low load may be less informative than a shorter, validated programme that reproduces the actual mechanism of damage.

“No visible damage means no loss of safety.”

Fibres, thread, coatings and interfaces can degrade internally. Residual-strength testing and microscopic inspection may reveal deterioration before it is obvious to the user.

“A recognised body-protector standard covers every strap used in equestrian equipment.”

Product standards have defined scopes. EN 13158 concerns specified protective jackets, body protectors and shoulder protectors; it should not be presented as a universal qualification for reins, girths, breastplates, lead ropes or other tack.

Building a practical test specification

A concise internal specification for an equestrian strap assembly should identify the product, intended use, material and hardware revision, loading direction, minimum and maximum force, load ratio, waveform, frequency, cycle target, environmental conditioning, sample quantity, fixture arrangement, instrumentation, inspection intervals and pass/fail criteria.

Photographs before, during and after testing are valuable, particularly when they show the first damage location. If possible, record force and displacement continuously, and note any sudden change in stiffness, hysteresis or slippage. Stop criteria should include not only rupture but also unintended release, excessive permanent deformation, sharp edges, abnormal noise, temperature rise and loss of adjustment.

The final report should make clear whether the result is a design qualification, a batch acceptance test, a comparison between prototypes or an investigation into a complaint. It should also state limitations. Test data are strongest when connected to traceability, production inspection, user instructions, field returns and a controlled programme of re-testing after design changes.

Conclusion

Cyclic fatigue testing is a way of asking the question that a one-off pull test cannot answer: what happens after the assembly has been used repeatedly, flexed around hardware, contaminated, adjusted and loaded in the directions that matter in practice?

The most defensible approach is to test the complete production assembly, reproduce the critical geometry and load path, combine cyclic loading with relevant environmental and abrasion conditioning, inspect function as well as appearance, and measure residual strength where appropriate. Results should be reported with enough detail to distinguish a meaningful engineering claim from a general durability assertion.

For users, the practical lesson is equally important: a high-quality strap is not defined by webbing strength alone. Buckle geometry, stitching, attachment reinforcement, material compatibility, inspection instructions and evidence from representative testing all contribute to the safety margin.

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

Sources and further reading

• ASTM International, ASTM D6770-21: Standard Test Method for Abrasion Resistance of Textile Webbing.
• EN 13158:2018, Protective clothing for equestrian use—requirements and test methods.
• International Organization for Standardization, ISO 2411:2024: Rubber- or plastics-coated fabrics—determination of coating adhesion.
• UK Health and Safety Executive, Using personal protective equipment to control risks at work: product safety and supply.
• Office for Product Safety and Standards, Personal Protective Equipment (Enforcement) Regulations 2018.
• Office for Product Safety and Standards, Product safety advice for businesses.
• British Equestrian Trade Association, BETA 2018 Standard for Body and Shoulder Protectors.
• SAE International, J339: Seat Belt Hardware Webbing Abrasion Test Procedure.

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