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 characteristics 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, additive additions, and colors 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
Determination of characteristic values of thermoplastics according to DIN EN ISO 527 on tension rod type 1A
- 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
- Optical and mechanical extensometer also enables determination of Poisson’s ratio/transverse contraction number
- Material data determination for CAE applications
Important tool for determining 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 the in-house technical center
If you do not have a test specimen tool available, we can produce test specimens from almost all common thermoplastics in our injection molding department. We can process all generally injection-moldable thermoplastics including high-temperature materials such as PPS, PEEK, PK, etc. Our range of services also includes the processing of carbon fiber or glass fiber reinforced as well as filled plastics. In addition, tensile bars can also be milled or punched from plates in our tool shop. We offer the following specimen geometries:
- Production of 1A and S2 tension rods
- Production of weld line tie rods
To determine the weld line strength
- Milling S2 tie rods
- Punching S2 tension rods from elastomers
- Production of plates and milling of tension rods to determine direction-dependent material characteristics
- Variation of injection molding 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. Tests during development, e.g. in accordance with automotive standards, allow confirmation of whether a plastic can be used. Tests at high and low temperatures can be carried out in our thermal chamber.
- Tensile test at elevated temperatures
Our thermal chamber enables tests up to 250°C
- Tensile test at low temperatures
Tests even at low temperatures down to -40°C are possible on request
- Media and temperature storage
We investigate, also in combination, the influence of media and hot storage on the material properties
- Conditioning of test specimens
We also offer conditioning and characteristic value determination of test specimens. Especially for 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 groups of components using various clamping devices. This test is particularly useful for belts, hooks and snap connections. If necessary, special clamping fixtures can be manufactured to enable testing
- 2C 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.
Measurement setup and results
The tensile test is used to investigate the stress-strain behavior of plastics. The specimens, which have previously been injection molded or machined from a semi-finished product, are tested under uniaxial tensile loading (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 properties such as Young’s modulus (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 curve shapes for different material types are shown in Figure 2.