Mechanical material testing

Laboratory management

Prof. Dr. Volker Herrmann

Phone
+49 931 3511-8405
E-Mail
volker.herrmann[at]thws.de

Tasks

The laboratory for mechanical materials testing has equipment for sample preparation and devices for test methods that are typically carried out on polymer materials. This includes static, quasi-static, dynamic loads and shock/impact loads. The spectrum of testable materials ranges from soft, cross-linked elastomers and thermoplastic elastomers to thermoplastics and high-strength thermosets. 

Room

  • A.0.13 / A.1.20 

Devices

Equipment for sample preparation and specimen production

  1. Zwick universal testing machines for performing tensile, compression and    
    Bending tests with quasi-static, static and dynamic loading (maximum test load 100 kN), temperature range - 150 °C to 250 °C, Zwick makes, types 1474 and 1445 with DOLI control system
  2. Instron 5982 testing machine with video extensometer for determining the transverse contraction number
  3. Dynamic mechanical spectrometer, type Eplexor 150N, GABO
  4. Device for determining dimensional stability in heat according to
    Martens (DIN 53462) and Vicat (DIN 53460, ISOR 306, VDE 0302 on polymers)
  5. Manual pendulum impact tester for determining the impact and notched impact strength in the temperature range - 50°C to + 100°C as well as the impact tensile strength on standardized test specimens made of polymer materials
  6. Instrumented pendulum impact tester according to Charpy by Instron, CEAST 9050 (max. impact force 50 J)
  7. Device for determining the rebound elasticity of elastomers according to DIN 53512
  8. Device for determining the indentation hardness of plastics in accordance with DIN 53456
  9. Hardness testers for determining the hardness of elastomers according to
    Shore A or Shore D in accordance with DIN 53505 ISO 868 and ASTMD 2240
  10. Frank abrasion tester for determining the abrasion of elastomers according to DIN 53516
  11. Precision balance 2006MP, Sartorius
  12. Convection oven UFE550, make Memmert

Sample preparation

Figure 1: Milling machine for extracting test rods from plastic sheet material
Figure 1: Milling machine for extracting test rods from plastic sheet material
Figure 2: Various punching knives for removing test specimens from elastomer plates
Figure 2: Various punching knives for removing test specimens from elastomer plates
Figure 3: Device for removing ring-shaped samples from elastomer sheets
Figure 3: Device for removing ring-shaped samples from elastomer sheets

For test specimen production in accordance with current DIN standards, standardized test bars (tensile test 1B, 3-point bending, impact strength) can be milled from plastic sheet material (Fig. 1). Elastomer test specimens are usually punched from 2 mm thick sheets. Punching dies are available for the following test specimens: S1, S2, S3A bar, Graves tear strength, circular punching knives with different diameters as well as punching knives for strip specimens with different widths (Fig. 2). A ring cutting device is available for the production of test specimens for testing the tensile strength of rings (R1 standard ring) (Fig. 3). For the preparation of abrasion test specimens according to DIN, a corresponding device is used to cut out the specimens.

Fig. 4: Zwick 1474 universal testing machine with optical extensometers, temperature chamber and DOLI controller
Fig. 4: Zwick 1474 universal testing machine with optical extensometers, temperature chamber and DOLI controller

Measuring devices for materials testing

Two Zwick universal testing machines are available for recording stress/strain curves (Zwick 1445 and Zwick 1474 with optical extensometers, see Figures 4 and 5) with the latest electronic control and evaluation software from DOLI and load cells with measuring ranges from 1 to 100 kN.
With the existing test fixtures, tests can be performed in the tensile test (bar and ring), tensile tensile strength, 3-point bending and compression test. Thanks to the free programmability of the software, combined measurement cycles are also possible, such as testing the Mullins effect on carbon black-filled elastomers (Fig. 6). For high-strength thermoset materials, a universal testing machine from Instron with video extensometer for determining the cross-contraction index and a force measurement range of up to 100 kN is available (Fig. 7). 

Figure 5: Students in the practical course on mechanical materials testing of plastics
Figure 5: Students in the practical course on mechanical materials testing of plastics
Figure 6: Mullins effect on carbon black-filled elastomers
Figure 6: Mullins effect on carbon black-filled elastomers
Figure 7: Instron universal testing machine
Figure 7: Instron universal testing machine
Figure 8: Tensile test on an elastomer
Figure 8: Tensile test on an elastomer
Figure 9: Instron instrumented impact pendulum
Figure 9: Instron instrumented impact pendulum

The measurement of the (notched) impact strength of thermoplastics can be carried out using two Charpy impact pendulums, also with the option of the instrumented impact strength test (Instron, see Fig. 9). 

Hardness measurements can be carried out according to Shore (A and D) and the ball indentation method in accordance with EN ISO 2039-1. A sliding pendulum is available for measuring rebound resilience (Fig. 10). The abrasion resistance of elastomers can be measured in accordance with DIN ISO 4649 (Fig. 11). 

Figure 10: Push pendulum for measuring the rebound elasticity of elastomers
Figure 10: Push pendulum for measuring the rebound elasticity of elastomers
Figure 11: Device for measuring the abrasion resistance of elastomers according to DIN ISO 4649
Figure 11: Device for measuring the abrasion resistance of elastomers according to DIN ISO 4649
Figure 12: Eplexor spectrometer from GABO Qualimeter (100 N)
Figure 12: Eplexor spectrometer from GABO Qualimeter (100 N)

Dynamic-mechanical measurements, even at different temperatures (DMTA), can be carried out on a 100 N eplexor spectrometer from GABO Qualimeter (Fig. 12). This can be used to measure glass transition temperatures and melting ranges of thermoplastics. By applying the method at different temperatures and/or frequencies and amplitudes, it is possible to create master curves/relaxation time spectra and to investigate the b>Payne effect for filled elastomers.

To test the Softening temperature according to Vicat, a measuring device with three measuring stations and electronic data recording is available. Measurements can be recorded at the standard heating rates of 50 and 120 K/min.