Plastics Tensile Testing

Introduction

Plastic tensile testing is a critical process that supplies information for analyzing plastic materials’ mechanical properties, such as their toughness, flexibility, and resistance. Tensile testing helps to understand whether plastics will perform well under various stresses and conditions and, therefore, meet the needs and specifications required for multiple applications. The test provides critical properties like tensile strength, yield strength, and modulus of elasticity by applying controlled tensile forces on plastic samples. This helps in the material’s behavior prediction in practical cases. This article briefly discusses the importance of plastic tensile testing and its applications in industries for crucial material performance in the automotive, aerospace, and construction sectors.

Scope

Testing plastics under tension is essential to understand the mechanical properties of plastic materials, such as strength, elasticity, and durability. It ensures that the fundamental properties of tensile strength, yield strength, and modulus of elasticity are measured to ensure plastics are reliable in stress and meet requirements as desired specifications in various applications. Such testing is essential in diversified industries like automobile, aerospace, and construction, where material performance becomes critical to safety, quality, and efficiency.

Procedure

Measure the width and thickness at the center and each end of the gage length, within 5 mm of each end, of the flat specimens. One specimen from each sample may be measured for injection molded samples if previous testing has demonstrated variation between specimens in width and thickness to be less than 1%. For thin sheeting, such as films less than 1.0 mm, measure the width of specimens produced by a Type IV die since the distance between the cutting edges of the die in the narrow section. For all other specimens, measure the actual width of the center portion of the specimen unless it can be shown that the width is the same as the die’s dimensions within the given tolerances.

Measure the diameters of the rod specimens and the inside and outside diameters of the tube specimens to the nearest 0.025 mm at a minimum of two points 90° apart. For testing specimens of tubes, measurement should be done using plugs to avoid the possibility of errors.

Then, place the specimen in the grips of the testing machine so that the long axes are parallel to the grips. Then, the grips should be tightened as equally and firmly as possible without crushing the specimen in order not to cause slippage of the specimen during the test.

Attach the extensometer extension indicator after placing the specimen. To accumulate practically correct data, use a Class B-2 or higher extensometer for modulus measurement. End. After aligning the specimen, tensile testing will be carried out by gradually increasing the load to the fracture point in the specimen. The machine conducting the tests will be equipped to measure the load applied and the deformation accrued, from which the properties of the material’s mechanics will be obtained.

Sample Size

Usually, 5-10 specimens are considered for plastic tensile testing to get an accurate result from statistical consideration. However, in the case of injection-molded samples, only one specimen might be sufficient when earlier tests show that the dimensions stayed the same. 

Result

The result provides insights into tensile strength, yield strength, and modulus of elasticity of plastic. These results help predict material behavior under stress, ensuring its suitability for various applications.

Conclusion

Plastic tensile testing determines plastic materials’ strength, elasticity, and durability. Moreover, determining tensile strength, yield strength, and modulus of elasticity enables plastics to perform under stress in a known manner and stipulated specifications for those applications. This process is of prime concern in automotive, aerospace, and construction industries, as efficiency, quality, and safety all depend upon the performance of the materials.

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