Electronic Tensile Testing Machine Measures the Right-Angle Tear Strength of Films

This article explains how to measure the right-angle tear strength of films using an electronic tensile testing machine. During the test, a film specimen with a right-angle notch is clamped into the testing machine and stretched at a constant speed, while the machine records the changes in force during the tearing process. By analyzing the relationship between force and displacement and combining it with the specimen thickness, the tear strength can be calculated. The article details the equipment requirements, specimen preparation methods, specific operational steps, and data processing procedures. It also highlights the importance of factors such as specimen quality, clamping condition, and testing environment to ensure accurate and reliable results.

Introduction

In material property evaluation, the right angle tear strength of the film is a key indicator, reflecting the material's ability to resist tear propagation. With its high accuracy and controllability, the electronic tensile testing machine has become a common equipment for measuring this parameter. This paper aims to systematically expound the principles, methods, operation points and results analysis of the right angle tear strength of thin films using an electronic tensile testing machine, and provide technical reference for related testing work.

Test Principle:

Right angle tear strength testing is usually performed with reference to relevant standards. The basic principle is to place the prepared right-angled specimen in the upper and lower fixtures of the electronic tensile testing machine and stretch it at a constant speed. The tearing process begins at the right-angled notch of the specimen and extends in a specific direction. The testing machine recorded the change of force value during the tensile process in real time, and calculated the tear strength of the sample by analyzing the force-displacement curve. Its calculation formula can be expressed as:
$σ = \frac{F}{d}$
Among them, $σ$ Represents tear strength (unit: N/mm or kN/m), $F$ is the average or maximum force value recorded during the tearing process (in N), $d$ is the thickness of the specimen (unit: mm). The specific use of average force or maximum force is based on the standards implemented.

Equipment and specimens

The main equipment for the test is an electronic tensile testing machine, which should have sufficient force range and accuracy, and be equipped with a flat fixture suitable for the film to prevent slippage. Specimen preparation is carried out in strict accordance with standards, usually using special cutting knives to shape the film into a shape with a right-angled notch. The accuracy of specimen size directly affects the reliability of test results.

Test steps

The operation process should be standardized and orderly. First, measure the thickness of the specimen, at least near the right-angle notch and take the average. Secondly, the specimen is clamped symmetrically in the fixture to ensure that the tear start is located in the middle of the two fixtures, and the upper and lower surfaces of the specimen are parallel to the tensile direction. Set the test parameters, including the tensile speed (usually lower speeds, e.g., 200mm/min to 500mm/min, depending on the standard) and the necessary environmental conditions (e.g., temperature, humidity). Start the test until the specimen is completely torn. Repeatedly test a sufficient number of specimens to obtain statistically valid data.

Data processing

Extract key data from force-displacement curves. The tear strength of each specimen is calculated according to the criteria employed. Statistical results such as arithmetic mean, standard deviation, etc. are usually reported for all specimens. Analyzing the shape of the curve can sometimes also provide information about the tearing behavior of the material, such as whether it exhibits a stable tearing process.

Influencing factors

Test results are influenced by a variety of factors and need to be controlled to ensure data comparability.

Sample preparation	Cutting quality, notch accuracy
Clamping state	Neutrality, clamping force, whether it is slippery
Test speed	The tensile rate must comply with the standard
environmental conditions	Temperature and humidity can affect material properties
Equipment calibration	Accuracy of force sensors and displacement systems

Notes:

Pay attention to safety during operation to avoid clamp injuries. Before testing, confirm that the equipment is in good condition and calibrated. For films of different materials or thicknesses, it may be necessary to adjust the fixture type or clamping force. If the specimen breaks at the clamping site, the data is usually considered invalid and the clamping method or specimen preparation process should be checked.

Epilogue

It is a mature and effective method to determine the right angle tear strength of thin film by electronic tensile testing machine. By strictly following standard processes, controlling key influencing factors, and standardizing data processing, results can be obtained that accurately reflect the tear resistance of materials, supporting material development, quality control, and product application.

References

1. The test principle partly refers to the standard methods for testing the tearing properties of plastic films at home and abroad.
2. The equipment and specimen section synthesizes the requirements for instruments and sample preparation in the general technical literature for material mechanical property testing.
3. The analysis of influencing factors is based on a number of technical research summaries on the repeatability and reproducibility of thin film mechanical testing.