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 (to ensure the test specimen is positioned centrally). The universal testing/compression testing machine compresses the specimen positioned between the pressure plates at a speed of 2 inches/min (50,8 mm/min) by 25% of its initial thickness (to 75%). The ram then returns to its starting position (0%). This pre-loading process is repeated three times. During the final (third) cycle, the compressibility is determined by measuring the maximum force applied during this phase. This peak force is then divided by the area (cross-section) of the specimen. The result is expressed in kPa (kilopascals) (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 calculated as a percentage of the initial sample thickness, the testing machine automatically determines the sample height (thickness 0) at the start of the test (under preload). Based on this variable thickness, the QUASAR universal testing machine automatically moves to the different positions. Therefore, the sample thickness 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 manually calculate or configure the above result (formula editor not required). In the testing software LabTest This result is available for activation to determine the compression hardness. Select result no. 513 (tension at the end of the phase) and enter the measurement phases (cycle phase 3 and cycle phase 7).
The smallest GALDABINI can be used for the test 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.
