Flexibility Resistance and Durability Testing Service

Flexibility Resistance and Durability Testing Service – Comprehensive Evaluation of Flexural Fatigue, Bend Resistance and Crease Recovery for Materials and Components

As an ISO/IEC 17025 accredited independent testing laboratory, we offer specialised flexibility resistance and durability testing services to manufacturers, engineers, and quality assurance teams across the automotive, aerospace, textile, packaging, wire and cable, medical device, and industrial equipment sectors. Flexibility resistance – the ability of a material or component to withstand repeated bending, folding, creasing, or flexing without cracking, delamination, loss of electrical continuity, or structural failure – is a critical performance attribute for a wide range of products, from flexible cables and hoses to textiles, films, and protective coatings. Our test protocols simulate the repetitive mechanical stresses encountered during service, storage, and handling, providing quantitative data on flex life, crease recovery, and fatigue resistance. All methods are aligned with ISO, ASTM, EN, and GB standards, including ISO 6722 (Road vehicles – 60 V and 600 V single‑core cables – Test methods), ASTM D2176 (Folding endurance of paper by the MIT tester), ISO 7854 (Rubber‑ or plastics‑coated fabrics – Determination of resistance to damage by flexing), ASTM D3212 (Flex resistance of coating films), and GB/T 12586 (Rubber‑ or plastics‑coated fabrics – Determination of resistance to damage by flexing). Our reports are recognised by national regulatory authorities, international certification bodies, and major industry buyers for product qualification, type approval, and quality assurance.

Materials and Products We Regularly Test

Our flex durability laboratory accommodates a wide range of material types and finished products. Typical test articles include:

• Wire and cable assemblies – automotive and aerospace cables, flexible cables, ribbon cables, and wire harnesses
• Textiles and coated fabrics – rubber‑coated and plastic‑coated fabrics, tarpaulins, inflatable structures, and protective clothing
• Films, sheets and laminates – polymer films, flexible packaging films, metal‑polymer laminates, and release liners
• Paper and paperboard – packaging materials, folding cartons, and printing papers
• Flexible composites – laminated composites for aerospace, marine, and automotive applications
• Protective coatings and paint systems – coatings for flexible substrates (e.g., automotive interior skins, elastomeric coatings)
• Gaskets, seals and diaphragms – elastomeric seals, rubber diaphragms, and flexible gaskets
• Medical devices – catheter tubing, flexible endoscope components, and surgical glove materials
• Plastic pipes and hoses – flexible hoses for hydraulic and pneumatic systems

Flex Fatigue and Repeated Bending Tests – Simulating Continuous Flexing

• MIT folding endurance test – ASTM D2176 / ISO 5626 / GB/T 2679.5 – for paper, paperboard, films and thin sheets – We use the MIT folding tester to apply a constant tension (typically 1 kgf or 9.8 N) to a narrow strip of material (typically 15 mm wide) and fold it repeatedly through a 135° or 180° angle until failure (fracture, delamination, or loss of strength). The number of double‑fold cycles to failure is recorded as the folding endurance. The test is performed at a specified humidity and temperature (typically 23 °C, 50 % RH). The MIT test is widely used for paper, plastic films, and thin metal foils.
• Flex endurance test for coated fabrics – ISO 7854 / GB/T 12586 – using a flexometer (De Mattia or similar) – We test rubber‑ and plastic‑coated fabrics by mounting a rectangular specimen (typically 100 mm × 200 mm) in a flexometer that repeatedly bends the specimen through a 90° or 180° angle at a specified rate (typically 100‑300 flexes per minute). The test is performed for a specified number of flexes (typically 100 000‑1 000 000), and the specimen is inspected for cracking, delamination, or loss of coating adhesion at specified intervals.
• Wire and cable flex test – ISO 6722 / SAE J156 / GB/T 2951.14 – for automotive and aerospace cables – We mount the cable in a flexing apparatus that moves the cable back and forth over a mandrel of specified diameter (typically 5‑10× the cable diameter) at a specified speed (typically 10‑30 cycles per minute). The test is performed until failure (conductor breakage, insulation cracking, or loss of electrical continuity) or until a specified number of flex cycles (typically 10 000‑100 000) is reached. The electrical resistance is monitored during the test to detect conductor breakage.
• Bend and reverse‑bend test – ASTM E290 / ISO 7438 – for metallic wires and strips – We bend a metallic specimen through a 90° or 180° angle and then bend it back in the reverse direction. The process is repeated until failure (cracking or fracture). The number of reverse‑bend cycles to failure is a measure of the material's ductility and resistance to fatigue. This test is particularly relevant for spring steels, wire products, and electrical contacts.
• Flex fatigue at elevated or reduced temperatures – for service‑simulating conditions – We perform flex endurance testing at elevated temperatures (e.g., 70 °C, 100 °C) using an environmental chamber, or at low temperatures (e.g., -40 °C) to simulate the service conditions for automotive and aerospace components. The test results at the specified temperature are compared to the room‑temperature results to determine the temperature sensitivity of the flex resistance.

Flexural Fatigue and Stress Cracking Tests – Assessing Material Degradation

• Flexural fatigue test – ASTM D7774 / ISO 178 – for assessing the fatigue life of plastics under bending – We apply a cyclic bending load (sinusoidal or other waveform) to a rectangular or cylindrical specimen at a specified stress amplitude and frequency. The test is performed until failure (fracture, excessive deflection, or loss of stiffness) or until a predetermined cycle count (typically 10⁶‑10⁷ cycles) is reached. The fatigue life (Nf) and the fatigue limit (the stress amplitude that allows infinite life) are determined, and an S‑N curve is generated.
• Flexural stress cracking test – ASTM D1693 / ISO 22088 – for assessing environmental stress cracking (ESC) in plastics – We apply a controlled flexural stress to a notched specimen (typically a bent strip or a constant‑strain test piece) and expose it to a specified environment (e.g., a surfactant solution, oil, or water). The time to cracking (or the number of cycles to cracking in a cyclic test) is recorded. The test is used to evaluate the resistance of plastics to environmental stress cracking, which is a common failure mode for flexible plastic parts.
• Crease recovery test – ASTM D1295 / ISO 2313 – for textiles and leather – We form a crease in the specimen (by folding it under a specified load for a specified time) and then measure the angle of recovery after the load is removed. The crease recovery angle is a measure of the material's elasticity and its ability to recover from folding without permanent damage.

Test Methods for Specific Applications – Cables, Textiles and Packaging

• Cable flex life and bend resistance – UL 62 / EN 60794 – for flexible cords and cables – For flexible cords and cables, we perform a flex life test using a reciprocating flexing apparatus (e.g., a drag‑chain or a cable trolley) that moves the cable back and forth over a specified path at a specified speed. The test is performed until failure (conductor breakage, insulation failure, or loss of continuity) or until a specified number of cycles is reached. The test is used for the qualification of cables for moving applications, such as robot cables, elevator cables, and drag‑chain cables.
• Textile and coated fabric flex resistance – ISO 5981 / ASTM D3885 – for coated fabrics and tarpaulins – We test the flex resistance of coated fabrics by subjecting the specimen to a combined flex and abrasion action using a flexometer. The test is performed at a specified flexing rate (typically 100 flexes per minute), and the specimen is inspected for coating cracking, fabric tearing, or coating delamination.
• Packaging and paperboard folding endurance – TAPPI T511 / ISO 5626 – for folding cartons and corrugated board – For folding cartons and corrugated board, we perform an MIT folding endurance test or a similar flex test to assess the ability of the material to withstand repeated folding without cracking or losing strength. The test is used for packaging materials that are subject to repeated folding during use (e.g., folding cartons, display boxes).
• Film and laminate flex test – ASTM D2454 / ISO 8762 – for flexible packaging films and laminates – We test flexible packaging films and laminates by repeatedly bending the specimen through a 180° angle at a specified rate and inspecting for creasing, cracking, or delamination. The test is performed on both the as‑received material and on samples that have been aged (to simulate shelf‑life).

Data Analysis and Interpretation – Quantifying Flex Life and Fatigue

• Flex life (number of cycles to failure) – the primary output of the test – The flex life is the number of flex cycles (or bending cycles) that the specimen can withstand before failure. The flex life is reported as the average of multiple specimens, along with the standard deviation and the coefficient of variation (CV).
• Fatigue life (Nf) and S‑N curve – for flexural fatigue tests – For flexural fatigue tests, we plot the stress amplitude (S) against the fatigue life (Nf) to generate an S‑N curve. The curve is used to estimate the fatigue limit (the stress amplitude that allows infinite life) and to predict the life of the component under a given service stress.
• Visual assessment and rating – for crack density and severity – For coated fabrics and painted surfaces, we assess the damage by counting the number of cracks per unit area (crack density) and by rating the crack severity (e.g., superficial, deep, or complete). A standardised rating system (e.g., a 0‑5 scale) is used to compare the results across different materials.
• Electromagnetic and electrical continuity monitoring – for cables and wires – During the flex test, we continuously monitor the electrical resistance (for cables and wires) using a resistance meter (or a continuity tester). A sudden increase in resistance or an open circuit indicates conductor breakage, which is recorded as the end of the test.

Regulatory Compliance and Product Certification – Supporting Industry Standards

Our flexibility resistance and durability testing services are performed in accordance with the most widely used international and national standards. The most commonly requested include:

• ASTM D2176 – Standard Test Method for Folding Endurance of Paper and Paperboard by the MIT Tester – for paper and paperboard
• ISO 7854 – Rubber‑ or plastics‑coated fabrics – Determination of resistance to damage by flexing – for coated fabrics
• ISO 6722 – Road vehicles – 60 V and 600 V single‑core cables – Test methods – for automotive cables
• UL 62 – Flexible Cords and Cables – for flexible cord and cable qualification
• ASTM D7774 – Standard Test Method for Flexural Fatigue Testing of Plastics – for flexural fatigue of plastics
• ISO 5626 – Paper – Determination of folding endurance – for folding endurance
• GB/T 12586 – Rubber‑ or plastics‑coated fabrics – Determination of resistance to damage by flexing – the Chinese national standard for coated fabrics
• GB/T 2679.5 – Paper and board – Determination of folding endurance – MIT method – the Chinese national standard for paper

Report Acceptance and Regulatory Recognition

All flexibility resistance and durability tests are conducted under our ISO/IEC 17025 accreditation, using calibrated flexometers, fatigue testers, and environmental chambers, all traceable to national and international reference standards. Our final test reports include: a complete description of the test article (material, dimensions, manufacturer), the test method and conditions (flex angle, flex rate, temperature, humidity, load), the measured parameters (flex life, fatigue life, crack density, resistance change, crease recovery angle), a statistical summary (mean, standard deviation, CV), and a clear pass/fail verdict against your specified acceptance criteria. These reports are accepted by the National Medical Products Administration (NMPA), the State Administration for Market Regulation (SAMR), the Ministry of Industry and Information Technology (MIIT), and international certification bodies for product registration, type approval, and quality assurance. Bilingual (Chinese/English) versions are available to facilitate submissions to domestic and international authorities and to support your global market access.