Mechanical Testing
Test Methods for Mechanical Properties of Materials
Mechanical properties must be checked and frequently verified after aging tests. These tests ensure that products withstand the requirements under real operating conditions throughout their entire lifecycle.
Tensile Strength, Flexural Strength
In a tensile test (destructive material testing) according to DIN EN ISO 527-1, the force and elongation of a sample are measured as a function of the applied strain. The measurement can also be performed at a defined temperature (-35 to +250 °C). The tensile test serves to determine the modulus of elasticity, tensile strength, and elongation at break of a material. Changes in these material properties after artificial aging or exposure to media are also of interest.
In a flexural test, the sample is subjected to quasi-static stress by compression. In the 3-point bending test (DIN EN ISO 178), the test specimen is positioned on 2 supports and loaded in the middle with a test punch. Applications here include the determination of flexural modulus, flexural strength, etc.
Impact Strength / Notched Impact Strength
In an impact test, the resistance of a material to impact (dynamic) stress is determined. In the notched impact test, the workpiece may be provided with a notch before the test, creating increased stress concentrations at the notch. A pendulum hammer with a certain kinetic energy strikes the back of the sample, breaking it. This test can also be performed at defined temperatures. Low temperatures increase the brittleness of the material (cold brittleness). Depending on the geometry, tests are distinguished according to Charpy (DIN EN ISO 179-1) and IZOD (DIN EN ISO 180).
Compression Set
The compression set according to DIN EN ISO 1856 is an important characteristic for elastomers, which are used, for example, as seals. The test specimen is first compressed to a certain percentage of its thickness and fixed at constant compression. This state is maintained for a defined period, during which additional influencing factors, such as elevated temperature, can act on the test specimen. After unloading, the permanent deformation is measured. If the remaining compression set is too high, the seal’s effectiveness could be impaired.Tear Strength
In the tear propagation test, a defined defect is introduced into a test specimen, for example, by means of a knife cut. At this point, the specimen is then loaded, and the force is measured during crack propagation. The measured force provides information about the material’s crack resistance. The test is usually performed according to DIN ISO 34-1 on elastomers for seals and according to DIN EN ISO 8067 on foams.Adhesion and Peel Strength
Peel strength, i.e., the resistance of a sheet material to detachment, is particularly relevant for films, nonwovens, carpets, upholstery fabrics, and adhesive tapes. Depending on the application and test standard, the adhesive force can be peeled off at a peel angle of 180°, 90°, or a freely selectable angle. Similarly, roller devices can be used to maintain defined peel angles, for example, in the roller peel test according to DIN EN 1372 with a 90° peel angle or in DIN EN 1464 with an approximately 60° peel angle.