Measurement of the tear initiated on a dynamometer

The initiated tear measurement is a mechanical test used to evaluate a material's resistance to the propagation of a pre-existing crack or tear. Performed using a dynamometer, this test is essential for characterizing the mechanical properties of plastic films, textiles, rubbers, composite materials, and flexible packaging.

It is a key indicator of durability, safety and performance for products subjected to mechanical stress during use or processing.

Principle and objectives of the initiated tear test

The test measures the force required to propagate a tear initially initiated in a material. This force reflects the material's ability to resist sudden rupture, a critical phenomenon in the case of packaging or technical materials.

The main objectives of this test are:

• Evaluate the mechanical resistance to crack propagation;
• Characterize the toughness and flexibility of the material;
• Compare the quality or formulation of different batches or suppliers;
• Verify compliance with technical and normative specifications;
• Optimize the design of packaging products to guarantee their integrity under conditions of use.

This test is particularly useful for identifying manufacturing defects, local weaknesses or variations in properties related to transformation processes (extrusion, drawing, rolling, etc.).

Standardized methods and test procedure

The initiated tear test is carried out on a universal tensile dynamometer equipped with a specific device depending on the type of material analyzed.

The main reference standards include:

• ISO 34-1 : Vulcanized or thermoplastic rubbers — Determination of tear resistance;
• ISO 6383-2 / ASTM D1938 : Plastic films — Propagating tear test (initiated hole);
• ASTM D624 : Rubbers — Determination of tensile strength.

The test protocol typically includes:

1. The preparation of a rectangular sample with a priming slit ;
2. Fixing the sample in the dynamometer;
3. Applying a tensile force at constant speed until the tear has fully propagated;
4. Recording of the force-displacement curve , the maximum of which corresponds to the tear resistance (expressed in N/mm).

Industrial applications

This test is widely used in various industrial sectors:

• Plastic and flexible packaging : evaluation of the resistance of packaging films, bags, stretch films, etc.;
• Technical textiles : testing the resistance of non-woven fabrics, membranes and geotextiles;
• Rubbers and elastomers : qualification of seals, coatings or membranes;
• Composite materials : measurement of cohesion and interlaminar strength;
• Automotive and aeronautical sector : validation of the mechanical strength of films, sheaths and flexible materials.

This test contributes directly to improving mechanical performance, the reliability of finished products and compliance with industrial specifications.

Interpretation of results and quality assurance

The results are expressed in newtons per millimeter (N/mm) and can be correlated with the material's composition, molecular orientation, or processing conditions.
A high value indicates good resistance to tear propagation, a sign of a ductile and strong material, while a low value reflects increased brittleness.

At YesWeLab , tests are conducted in ISO 17025 accredited laboratories , following rigorous protocols that guarantee the reproducibility and traceability of results. Reports include:

• The test conditions (temperature, speed, type of specimen);
• The stress curve as a function of displacement;
• Technical interpretation of the results by our experts.

YesWeLab Expertise and Support

YesWeLab provides a network of laboratories specializing in mechanical testing on materials and polymers , covering all quality control, design validation and physical characterization .

Our digital platform simplifies the management of your analyses: sample submission, online tracking, and report retrieval.
Our engineers will assist you in choosing the method best suited to your material and regulatory requirements (ISO, ASTM, EN).

Further analyses recommended

To complement the mechanical characterization of your materials, YesWeLab also offers:

• Tensile tests on polymers and films
• Bending and compression tests
• Measurement of puncture resistance
• Coating adhesion tests

These additional tests allow for a complete characterization of the mechanical and thermal behavior of flexible, polymeric and composite materials.