Tensile test, stress-strain diagram cross-contraction number from room temperature to 250 °C
The “more” in application possibilities with the tensile test
Determination of material properties with the tensile test
The tensile test according to the standard DIN EN ISO 527 for plastics and DIN EN ISO 53504 or ISO 37 for elastomers and thermoplastic elastomers is one of the most important tests for determining material properties. A test specimen is loaded at a constant strain rate until it breaks. The resulting material properties are the most frequently used values for comparing materials. Tensile tests can be used to determine the effects of various processing parameters, additives and colours or previous storage on the mechanical properties of plastics.
Our range of services includes tests for a variety of applications:
- Tensile test at room temperature
Characteristic value determination of thermoplastics according to DIN EN ISO 527 on a type 1A tensile bar
- Tensile test on elastomers
Thermoplastic elastomers (TPE) are tested under special conditions according to ISO 37 or DIN 53504. The preferred test specimen according to DIN 53504 is the S2 tensile bar.
- Application in quality assurance
Comparison of different batches
- Mechanical extensometer also allows determination of Poisson’s ratio / Poisson’s ratio in a temperature range from 1°C to 200°C
- Material data determination for CAE applications
Important tool for the determination of material data for strength calculations and FE structure analyses (FEM). Creation of stress-strain diagrams or output of raw data
From granulate to measured value: test specimen production in our in-house technical centre
If you do not have a test specimen tool available, we can produce test specimens in our injection moulding department from almost all common thermoplastics. All generally injection-mouldable thermoplastics including high-temperature materials such as PPS, PEEK, PK etc. can be processed. Our range of services also includes the processing of carbon fibre or glass fibre reinforced as well as filled plastics. In addition, tension rods can also be milled or punched from plates in our toolmaking shop. We offer the following specimen geometries:
- Production of 1A and S2 tension rods
- Production of weld line tensile bars
For the determination of the weld line strength
- Milling of S2 tension rods
- Punching of S2 tension rods from elastomers
- Production of plates and milling of tension rods to determine direction-dependent material characteristics
- Variation of injection moulding parameters and production
Application-related material data determination for your project
In many applications, plastics are exposed to aggressive media or higher temperatures. These can have a strong impact on performance. The influence on the properties can be tested in serviceability tests. Development-accompanying tests, e.g. according to automotive standards, make it possible to confirm whether a plastic can be used. In our thermal chamber, tests can be carried out at high and low temperatures.
- Tensile test at elevated temperatures
Our thermal chamber allows tests up to 250°C
- Tensile test at low temperatures
Tests at low temperatures down to -70°C are also possible on request.
- Media and temperature storage
We investigate, also in combination, the influence of media and warm storage on the material properties.
- Conditioning of test specimens
We also offer conditioning and characteristic value determination of test specimens. Especially with polyamides, the influence of the moisture content can be determined.
- Tensile test on components or assemblies
For some applications it is necessary to determine the maximum force on the component. We can test components or assemblies with various clamping devices. This test is particularly useful for belts, hooks and snap connections. If necessary, special clamping fixtures can be manufactured to allow testing
- 2K test specimen
We also offer a test for testing adhesion in 2K systems. Here, a peel test specimen is tested in a fixture according to DIN En 1464.
Test set-up and results
The tensile test is used to investigate the stress-strain behaviour of plastics. The specimens, previously injection moulded or machined from a semi-finished product, are tested under uniaxial tensile stress (cf. Figure 1). The tensile testing machine records the relationship between stress and strain of the specimen in a stress-strain diagram by measuring the force and taking into account the specimen cross-section, as well as measuring the displacement.
The tensile test is used to determine typical material parameters such as modulus of elasticity, yield strength, tensile strength and elongation at break of materials. The modulus of elasticity is defined in the elastic range as the slope of the stress-strain curve in the range between 0.05% and 0.25% strain. Tensile strength is the maximum tensile stress recorded during the test. Typical curves for different material types are shown in Figure 2.
3-point bending test according to ISO 178
The 3-point bending test determines the bending properties of plastic samples. The standardised test specimen is placed on two parallel supports and loaded by means of a compression fin up to a certain elongation or until breakage. Characteristic values such as the bending modulus as well as stress and strain values are determined. The test can be carried out at room temperature or at higher temperatures.
Compression test according to DIN EN ISO 604
In addition to the compression tests on components, the tests can also be carried out on standard-specific test specimens.
In the compression test, the stress-compression behaviour of plastics under uniaxial compressive stress is examined.
The test specimen is compressed at a defined test speed and specific characteristic values such as the compression modulus, compressive strength and elongation are determined.