Company: TeMeCo
Determination of the short tensile strength of polymer matrix composites
ASTM D 2344
Polymer matrix composites (PMC) consist of a matrix of thermoset or thermoplastic material and embedded glass, carbon, steel or fibres.
As high-performance speciality materials, PMCs are of interest to scientists all over the world. Many tests have been documented in the literature to investigate the effects of the sample parameters on the strength of short bars. For example, a systematic study was conducted to investigate the effect of sample size on the interlaminar shear strength of unidirectional carbon fibre epoxy using the three-point short shear test.
The application of this test method is limited to continuous or discontinuous fibre-reinforced polymer matrix composites where the elastic properties are uniform and symmetrical with respect to the longitudinal axis of the beam.
ASTM D 2344 describes a method for measuring the strength of short beams based on the maximum load observed during the test and the measured specimen width and thickness. Therefore, five laminated PMC materials were analysed in this application report to determine the parameter of short beam strength.
Carrying out the experiment
Method
The following sample dimensions were used for the tests: Sample thickness approx. 5.5mm, width approx. 12mm. The support distance was 12mm and the punch diameter 10mm (instead of 6mm).
Equipment
- Universal testing machine Shimadzu AGX-V 50kN with load cell 50kN
- Software TrapeziumX-V Single, 3-point bending test
- Bending device TH103 for tests according to ASTM 2344 and ISO 14130
Results
The force-displacement curves for five laminated PMC samples are shown in the figure on the left. The measurement of the pre-force or the start of the displacement should be set to a higher value to enable a start at the same level.
The strength of short bars according to ASTM D 2344 can be easily determined with a Shimadzu universal testing machine in combination with a special device according to the standard. In this application report, a stamp diameter of 10 mm was used instead of 6 mm, which has a slight influence on the measurements. Overall, the results are within an acceptable and reproducible range.
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