Mechanical testing

Tensile strength, bending strength

In a tensile test (destructive material testing) according to DIN EN ISO 527-1, the force and change in length of a sample is measured as a function of the applied strain. This measurement can also be carried out under defined temperature (-35 to +250°C). The tensile test is used to determine the modulus of elasticity, tensile strength and elongation at break of a material. Changes in these material properties after artificial ageing or exposure to media are also of interest.

In a bending test, the sample is quasi-statically stressed by pressure. In the 3-point bending test according to DIN EN ISO 178, the test sample is positioned on 2 supports and loaded in the middle with a test stamp. Fields of application here are the determination of the bending modulus, the bending strength, etc.

Impact strength / notched impact strength

In an impact test according to DIN EN ISO 179-1, the resistance of a material to an impacting (dynamic) load is determined. In the notched impact test, the workpiece is provided with a notch before the test, whereby increased stress peaks occur at the notch. A pendulum hammer with a certain kinetic energy hits the back of the specimen and shatters it. This test can also be carried out at defined temperatures. Low temperatures increase the brittleness of the material (cold brittleness).

Compression set

The compression set is an important parameter for elastomers that are used, for example, as seals. The test specimen is first compressed to a certain proportion of the thickness and fixed at constant compression set. This state is maintained for a defined time, whereby additional influencing variables, such as increased temperature, can act on the test specimen. After unloading, the remaining deformation is measured. If the remaining compression deformation is too high, the seal could be limited in its effectiveness.

Tear propagation force

Limb tear propagation test Textiles

Particular importance is attached to the tear propagation strength of film packaging. The test according to ISO 34-1, ISO 6383-1, EN 495-2 and DIN 53363 simulates the film behaviour when a package is opened. Ideally, the tearing force and the tear propagation force are the same - so that a film bag can be opened in a controlled manner and the contents removed. If, on the other hand, the maximum force up to the tear of the sample is too high in comparison, this can lead to abrupt further tearing after the first tear. For the end consumer, this usually leads to an unintentional spilling and thus often to a loss of the contents. In addition, the packaging becomes unusable and resealing is impossible.