Tensile Breaking Force Testing: Comprehensive Determination of Tensile Strength and Breaking Force

Tensile breaking force testing is a fundamental mechanical evaluation method used to determine the maximum force a material can withstand before fracture under axial tension. This critical quality control and product certification procedure applies to plastics, textiles, rubber, metal wires, films, cables, and packaging materials across global manufacturing industries. This article provides a detailed technical overview of tensile breaking force determination, including applicable standards, sample types, testing procedures, and practical applications.

Tensile breaking force testing is a fundamental mechanical evaluation method used to determine the maximum force a material can withstand before fracture under axial tension. This critical quality control and product certification procedure applies to plastics, textiles, rubber, metal wires, films, cables, and packaging materials across global manufacturing industries. This article provides a detailed technical overview of tensile breaking force determination, including applicable standards, sample types, testing procedures, and practical applications.

Technical Overview

Tensile breaking force determination is a core mechanical property test that measures the resistance of a material to failure when subjected to a uniaxial pulling force. During the test, a specimen is clamped between two grips of a universal testing machine and stretched at a controlled constant speed until rupture occurs. The instrument records the force-extension curve, from which key parameters such as breaking force (maximum force at failure), tensile strength (maximum stress), and elongation at break are calculated.

This testing methodology is governed by internationally recognized standards published by organizations including ISO, ASTM, EN, GB, and JIS. The results provide essential data for material selection, product design, quality assurance, incoming material inspection, and compliance verification for regulatory and certification purposes. Testing is typically performed by accredited third-party laboratories using calibrated equipment traceable to national metrology institutes.

Testing Samples

Plastic Materials

Rigid and flexible plastics, including polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), ABS, polycarbonate (PC), and engineering plastics, are tested in the form of dumbbell-shaped (dog-bone) specimens machined or molded according to ISO 527 or ASTM D638 requirements.

Textiles and Fabrics

Woven, knitted, and nonwoven fabrics, yarns, threads, and webbing are tested using strip or grab methods as specified in ISO 13934-1/2, ASTM D5034, ASTM D5035, and GB/T 3923. Specimens are prepared with precise dimensions in both warp and weft directions.

Rubber and Elastomers

Vulcanized rubber, silicone, thermoplastic elastomers (TPE), and latex products are evaluated using dumbbell or ring specimens in accordance with ISO 37, ASTM D412, and GB/T 528.

Metal Wires and Cables

Steel wires, aluminum conductors, copper wires, wire ropes, and complete cable assemblies undergo tensile breaking force testing per standards such as ASTM A370, ISO 6892-1, GB/T 228.1, and IEC 60811-501 for cable conductors.

Films and Packaging Materials

Plastic films, laminates, sealing strips, adhesive tapes, tear tapes, and packaging belts are tested according to ASTM D882, ISO 1184, and related standards to evaluate mechanical integrity during handling and transportation.

Adhesives and Bonded Joints

Bonded assemblies, sealants, and adhesive joints are tested for cohesive and adhesive failure strength using lap-shear and butt-joint configurations per ASTM D1002 and ISO 4587.

Testing Items

• Maximum tensile breaking force (N, kN)
• Tensile strength (MPa) and tensile stress at break
• Elongation at break and elongation at maximum force (%)
• Yield strength and yield point elongation
• Tensile modulus (Young's modulus)
• Breaking tenacity for yarns and fibers (cN/tex)
• Seam slippage resistance and seam breaking strength for textiles
• Peel strength and bond strength for laminates and adhesives
• Proof stress and stress at specified elongation

Testing Methods

Equipment and Instrumentation

Testing is conducted using universal testing machines (UTM) equipped with load cells of appropriate capacity and accuracy class (typically ISO 7500-1 class 0.5 or class 1), interchangeable grips, and extensometers for strain measurement. The equipment must be regularly calibrated and verified to ensure measurement traceability.

Standard Test Procedures

The general test sequence involves specimen conditioning at standard atmosphere (typically 23°C ± 2°C and 50% ± 10% relative humidity), dimensional measurement of the specimen cross-section, proper gripping alignment to eliminate slack and bending, application of a pre-tension where required, and extension at a constant crosshead speed until rupture. Force-displacement data are continuously recorded throughout the test.

Commonly Applied Standards

• ISO 527-1/-2 / GB/T 1040 — Tensile properties of plastics
• ASTM D638 — Tensile properties of plastics
• ISO 13934-1/-2 / GB/T 3923 — Tensile properties of textile fabrics
• ASTM D5034 / ASTM D5035 — Breaking force and elongation of textiles
• ISO 37 / ASTM D412 / GB/T 528 — Tensile properties of vulcanized rubber
• ISO 6892-1 / ASTM E8 / GB/T 228.1 — Tensile testing of metallic materials
• ASTM D882 — Tensile properties of thin plastic sheeting and films
• IEC 60811-501 — Tensile test for cables and insulating materials
• ASTM D2256 — Tensile properties of yarn by single-strand method

Data Processing and Reporting

At least five valid specimens are normally tested for each direction or condition, and results are reported as arithmetic means with standard deviations. Invalid breaks occurring within the grip region are discarded and retested. The final report documents the standard applied, specimen dimensions, conditioning parameters, test speed, individual and mean breaking force values, calculated strength values, and a description of the failure mode.

Applications

Tensile breaking force determination serves a wide range of industries and purposes:

• Quality control and incoming material inspection in manufacturing plants producing plastic components, cables, textiles, and packaging
• Product certification and regulatory compliance for electrical cables, medical devices, automotive parts, and construction materials
• Research and development for new material formulation, compound optimization, and process validation
• Failure analysis to identify root causes of product breakage in service
• Supplier verification and batch acceptance testing between trading partners
• Verification of design safety factors for structural and load-bearing components

FAQ

What is the difference between breaking force and tensile strength?

Breaking force is the maximum force (in newtons) that a specimen sustains before fracture, while tensile strength is the maximum stress (in megapascals) calculated by dividing the breaking force by the original cross-sectional area of the specimen. Breaking force applies directly to materials tested in full section, such as wires and fabrics, whereas tensile strength is used for materials tested with machined or molded specimens.

How many specimens are required for a valid test?

Most standards specify a minimum of five valid specimens per sample direction or condition. For textiles, both warp and weft directions are typically evaluated with five specimens each. Specimens that break within the grips or slip during testing are considered invalid and must be replaced.

Why is specimen conditioning important?

Temperature and humidity significantly influence the mechanical behavior of plastics, textiles, and rubber. Conditioning specimens in a standard atmosphere before testing ensures reproducible and comparable results between laboratories and across different test dates.

How is the test speed selected?

The separation speed depends on the material and the governing standard. Plastics are commonly tested at 1 to 500 mm/min depending on the modulus classification, textiles at 20 to 100 mm/min, and metals at rates producing controlled strain rates. Using an incorrect speed can substantially alter the measured breaking force, so strict adherence to the standard is essential.

Can testing be performed on-site or at a manufacturer's facility?

Yes, portable tensile testers are available for on-site verification; however, results used for certification, export documentation, or dispute resolution should be generated by accredited third-party laboratories with calibrated equipment and validated test methods.