Crescent Specimen
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Crescent specimen
General
For the calculation of the tear propagation resistance in the tear propagation test, trapezoidal test specimens according to DIN 53363 as well as strip-, angle- and arc-shaped test specimens according to ISO 34-1 are used for films. The term “crescent test pieces” is also used in the literature.
Test specimen shape
In addition to the trapezoidal test specimen and the trouser specimen, the curved crescent test specimen is also used in testing practice.
Figure 2: Crescent specimen for calculation of the tear propagation resistance of elastomers
Determination of material parameter
During the stressing on the specimen, the load–elongation–diagram is registered. The tear propagation resistance Ts is calculated after the evaluation of the registered load–elongation–diagram with help of the maximum load FM as well as the median of load (force) and the specimen thickness B:
The material value, which is calculated by this method, allow comparing different materials. For polymers it is dependent on:
- the material quality and load case,
- the preferred direction because of the moulding process of thermoplastic polymers,
- the curing time at elastomers and
- the testing temperature and the deformation velocity
See also
References
- Grellmann, W., Seidler, S. (Eds.): Polymer Testing. Carl Hanser Munich, 3rd. Edition (2022 ) p. 124 (ISBN 978-1-56990-806-8; e-book 978-1-56990-807-5; see AMK-Library under A 22)
- DIN 53363 (2003-10): Testing of Plastic Films – Tear Test using Trapezoidal Test Specimen with incision (withdrawn; replaced by DIN EN 17679:2022-08)
- DIN EN 17679 (2022-08): Plastics – Plastic Films – Determination of Tear Resistance using a Trapezoidal Test Specimen with Incision
- ISO 34-1 (2022-06): Rubber, Vulcanized or Thermoplastic – Determination of Tear Strength – Part 1: Trouser, Angle and Crescent Test Pieces
- ASTM D 624 (2000, reapproved 2020): Standard Test Method for Tear Strength of Conventional Vulcanized Rubber and Thermoplastic Elastomers