Foam compression test according to ASTM D 1056 | Compression hardness test
compression deformation of foam
Determination of the compression hardness of elastic foams
This test is used to determine the compression hardness of elastic foams. The sheet material is compressed by 25% (to 75%) and 50% (to 50%) of the initial sample thickness. This test is carried out according to the ASTM D1056 standard.
A sample with a diameter of 29 mm, cut out using a crown drill, is placed between two pressure plates. The thickness of the material should be greater than 6 mm. A 500 N load cell or similar should be provided for the force measurement.
The pressure plates should have centering grooves (in order to be able to insert the test piece centrally). universal testing machine / Compression testing machine compresses the sample positioned between the compression plates at a speed of 2 inches/min (50,8 mm/min) by 25% of the initial sample thickness (to 75%). The punch then returns to the starting position (0%). This preload is repeated 3 times. In the last (3rd cycle) the compressibility is determined by determining the maximum value of the force in this phase. This peak force value is divided by the area (cross section) of the sample. The result is given in kPa (kilo Pascal) (1 kPa = 1000 Pa = 0,1 N/cm²).
In the further course of the test, after this 3rd cycle, the sample is again unloaded and then the test described above is repeated for a compression height of 50%. In the last cycle (3rd cycle for 50% compression), the compressibility is determined as before.
Since the compression path must be approached in % in relation to the initial sample thickness, the testing machine automatically determines the sample height (thickness 0) at the start of the test (at preload). In relation to this variable thickness, the universal testing machine QUASAR the different positions automatically. The thickness of the sample does not need to be measured and entered manually beforehand. Simply press start and the test runs fully automatically.
| formula for compression hardness | CD% = F% / ((dxd) x ? ) / 4) |
| CD25% | compression hardness at 25% compression travel |
| CD50% | compression hardness at 50% compression travel |
| F25% | force at 25% compression distance |
| F50% | force at 50% compression distance |
| d | sample diameter |
Note:
It is not necessary to calculate or configure the above result manually (formula editor not required). This result is available for activation in the LabTest testing software to determine the compression hardness. Select result no. 513 (stress at the end of the phase) and enter the measurement phases (cycle phase 3 and cycle phase 7).
For the test, the smallest GALDABINI universal testing machine QUASAR 2,5 kN Instead of the standard 2500 N load cell, a 500 or 1000 N load cell is recommended. Very simple, inexpensive pressure plates made of aluminum Ø 96 mm can be used for the pressure test.
