Tearing Strength Testing Methods: Principles, Standards, and Procedures

Tearing strength testing measures a material's resistance to the propagation of an initiated tear and is a cornerstone of quality control for textiles, plastic films, rubber products, and coated fabrics. This guide explains the principles of tear testing, the major ISO, ASTM, EN, GB, and JIS test methods, specimen requirements, and how to select the right method for different materials.

Technical Overview

Tearing strength, also referred to as tear resistance or tear force, is a fundamental mechanical property that describes the ability of a material to resist the growth of an existing cut or slit. Unlike tensile strength, which measures the force required to break an intact specimen, tear testing measures the force or energy required to propagate a deliberately initiated tear under controlled conditions. Because many products fail in service through tear growth rather than through clean tensile fracture, this property is a critical quality, safety, and durability indicator.

A typical tear test involves preparing a specimen of standardized geometry, introducing a precise slit or notch, and applying force using either a pendulum-type (ballistic) instrument or a constant-rate-of-extension universal testing machine. Depending on the governing standard, results are expressed as tear force in newtons (N), tear energy in millinewtons (mN) or gram-force (gf), or tear strength normalized by thickness in kilonewtons per metre (kN/m). The principal standardization organizations publishing tear test methods include ISO, ASTM International, CEN (EN standards), the Chinese national standards system (GB), and JIS.

Testing Samples

Rubber and Thermoplastic Elastomers

Vulcanized rubber compounds and thermoplastic elastomers (TPE/TPV) used for seals, hoses, diaphragms, conveyor belts, and tire components. Tear testing of these materials is generally governed by ASTM D624 and ISO 34-1, with typical test piece thicknesses of approximately 2 mm.

Plastic Films and Sheeting

Mono-layer and multilayer films of PE, PP, PET, PA, and other polymers up to roughly 250 µm in thickness, including flexible packaging laminates, shrink films, and heavy-duty sacks. Relevant methods include ASTM D1004, ASTM D1922, ASTM D2582, and the ISO 6383 series.

Textiles and Nonwovens

Woven and knitted apparel fabrics, home textiles, industrial fabrics, and nonwoven materials. Tear performance is commonly evaluated using ASTM D1424, ASTM D2261, ASTM D5587, and the ISO 13937 series, or the equivalent GB/T 3917 series.

Coated Fabrics

PVC- or PU-coated textiles used for tarpaulins, tents, awnings, inflatable structures, and protective clothing, typically tested under the ISO 4674 series or related national adoptions.

Paper, Leather, and Geotextiles

Paper and paperboard evaluated by pendulum tear methods such as ISO 1974, leather and synthetic leather for footwear and upholstery, and geotextiles, for which the trapezoid method under ASTM D4533 is widely applied.

Testing Items

Accredited third-party laboratories routinely perform the following tear determinations:

• Elmendorf (ballistic pendulum) propagating tear resistance
• Graves tear resistance of plastic film and thin sheeting
• Trouser tear strength
• Angle test piece tear strength
• Crescent test piece tear strength
• Delft (small test piece) tear strength
• Tongue tear force, single rip and double rip procedures
• Wing tear force
• Trapezoid tear force
• Puncture-propagation tear resistance
• Directional tear evaluation, such as machine direction (MD) versus transverse direction (TD), or warp versus weft

Testing Methods

Elmendorf Pendulum (Ballistic) Method

A rectangular specimen is clamped in a fixed jaw and a movable jaw of a pendulum apparatus, and a standardized slit is cut into the specimen. When the pendulum is released, the energy stored in the raised pendulum is partially absorbed by tearing the specimen along a fixed path. The difference in pendulum energy before and after the tear is converted into tear resistance, usually reported in mN or gf. This rapid, economical method is specified in ASTM D1424 (fabrics), ASTM D1922 (plastic films), ISO 13937-1 (textiles), ISO 6383-2 (films), and the corresponding GB/T 3917 and GB/T 16578.2 standards.

Trouser Tear Method

A rectangular specimen is cut lengthwise at one end to form two legs resembling a pair of trousers. The legs are gripped separately and pulled apart at a constant crosshead speed, and the force required to propagate the tear along the cut is recorded. Because the tear path is well defined, the method is particularly useful for thin films and elastomers. It is specified in ISO 6383-1 (plastic film), ISO 13937-2 (textiles), the trouser geometry of ISO 34-1 and ASTM D624 (rubber), and GB/T 16578.1.

Angle (Graves) Method

An angle-shaped specimen containing a precise nick at the apex of the angle is stretched in a universal testing machine. The stress concentration at the notch tip initiates the tear, and the maximum force recorded is used to calculate tear strength. The Graves geometry is the basis of ASTM D1004 for plastic film and sheeting and corresponds to the angle test piece described in ISO 34-1 for rubber.

Crescent Method

A crescent-shaped specimen with a small nick or slit is stretched until the tear propagates through the narrowed cross-section. This geometry, described in ISO 34-1 and ASTM D624 for vulcanized rubber and thermoplastic elastomers, produces a single, sharp tear front and yields reproducible peak force values.

Delft (Small Test Piece) Method

When only a limited amount of material is available, for example when cutting specimens from finished rubber articles, the small Delft test piece defined in ISO 34-2 may be used. The procedure follows the same principle as the angle or trouser test but on a reduced scale.

Tongue (Single and Double Rip) Method

A rectangular slit is cut in the center of the specimen to form a tongue. In the single rip procedure (ASTM D2261), the tongue is clamped in the upper jaw and the body of the fabric in the lower jaw; as the jaws separate, the tear propagates down both sides of the tongue. In the double rip procedure (ISO 13937-4), both cut tails are clamped together in one jaw. These constant-rate-of-extension methods record tear force peaks, from which median or maximum values are derived.

Wing Method

Described in ISO 13937-3, the wing-shaped specimen modifies the tongue concept with angled cut edges so that the tear lines align with the direction of applied force. This improves tear path stability for coated and technical fabrics where a standard trouser test may deviate from the cut line.

Trapezoid Method

A trapezoidal specimen is marked with clamping lines along the two non-parallel sides, and a small initial slit is cut at the center of the shorter side. The fabric is clamped along the marked lines so that the region near the slit remains slack, and the force needed to propagate the tear is measured on a universal testing machine. The method is favored for nonwovens (ASTM D5733), woven and coated fabrics (ASTM D5587, ASTM D751), and geotextiles (ASTM D4533).

Puncture-Propagation Method

Specified in ASTM D2582, this dynamic test uses a falling pendulum carrying a tearing probe that punctures the film and propagates a tear in a single motion. The energy absorbed is reported as puncture-propagation tear resistance, making the method suitable for heavy-duty packaging films such as sack materials that experience combined puncture and tear loads in distribution.

Sample Preparation and Conditioning

Regardless of the method, specimens must be die-cut cleanly without nicks or fraying, and the initiating slit or notch must be cut with a sharp blade to precise dimensions. Textile specimens are conditioned in a standard atmosphere, for example 20 °C and 65% relative humidity per ISO 139, while films and rubber are commonly conditioned at 23 °C and 50% relative humidity as specified in the individual method. Testing in both principal directions of anisotropic materials is essential, since tear resistance often differs significantly between machine and transverse directions or between warp and weft.

Applications

Tearing strength data support design, specification, and regulatory compliance across many industries:

• Flexible packaging: verifying tear performance of laminates, shrink films, and sacks for both openability and transport durability
• Automotive: qualifying interior trim fabrics, seat covers, airbag materials, seals, and hoses
• Personal protective equipment and medical devices: evaluating gloves, gowns, surgical drapes, and barrier fabrics where a tear could compromise protection
• Outdoor and technical textiles: assessing tents, tarpaulins, awnings, sails, and coated architectural membranes
• Civil engineering: quality control of geotextiles used in separation, filtration, and reinforcement layers
• Footwear and leather goods: tear resistance of uppers, linings, and synthetic leather materials
• Paper and converting: characterizing printing papers, packaging paperboard, and tissue products

FAQ

What is the difference between tear strength and tensile strength?

Tensile strength measures the force needed to break an intact, uniform specimen, while tear strength measures the force or energy required to propagate an existing cut or slit. A material can exhibit high tensile strength yet low tear resistance, which is why both properties are usually evaluated together.

Which tear method should be selected for plastic film?

For thin films, ASTM D1004 (Graves) evaluates tear resistance at a slow extension rate, ASTM D1922 (Elmendorf) measures rapid propagating tear, ASTM D2582 evaluates combined puncture and tear, and ISO 6383-1 (trouser) suits thicker or more extensible films. Method selection should follow the product specification or end-use requirement.

Why must specimens be tested in both directions?

Films and fabrics are anisotropic: molecular or yarn orientation causes tear resistance to differ between machine and transverse directions or between warp and weft. Testing both directions reveals the weaker orientation, which typically governs service performance.

What units are used to report results?

Elmendorf tests are reported in mN or gf, fabric tear tests in newtons (N) as median or peak tear force, and rubber tear strength is normalized by thickness and reported in kN/m. The reporting convention must always follow the governing standard.

How many specimens are required?

Most standards require a minimum of five valid specimens in each test direction, with additional testing if results show excessive variability or if individual tear values fall outside specified limits.

Can finished products be tested?

Yes. When specimen size is limited, small-scale geometries such as the Delft test piece in ISO 34-2 allow tear evaluation directly on components cut from finished articles, subject to the dimensional requirements of the standard.