Interlaminar Shear Strength
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Interlaminar shear strength
Short-beam bend test
For determining the interlaminar shear strength (ILSF) of fiber-reinforced composites, the short beam test is used as a typical method for quality assurance. Fig. 1 shows a test device (Wyoming Test Fixture) with test specimen as an add-on unit for a universal testing machine, which can be used in three- and four-point bending systems (see: bend test).
| Fig. 1: | Test equipment with test specimen for short-beam bend test |
Determination of characteristic parameters
The apparent shear strength determined by the short bend test is the maximum shear stress present in the neutral fiber of the test specimen at the moment of the first failure. The resistance to interlaminar shear stress is determined parallel to the layers of the laminate, which provides information on the fiber/matrix bonding. The test can be carried out in accordance with ASTM D 2344, DIN EN 2563 or ISO 14130, which differ in the required L/D ratio, the test specimen length, the support dimensions and the test velocities. The schematic representation of the test arrangements and the test specimen geometries are shown in Figures 2 a and b as well as c.
| Fig. 2: | Schematic representation of the short beam test according to ASTM D 2344 (a), DIN EN 2563 (b) and ISO 14130 (c) |
Interlaminar shear strength (ILSF)
The interlaminar shear strength is calculated according to the following equation.
with
| F | compression load | |
| B | width | |
| d | thickness |
This test is suitable for the quality monitoring of sheared components since only small test specimens have to be machined out.
See also
References
- ASTM D 2344/ D 2344 M (2022): Standard Test Method for Short-Beam Strength of Polymer Matrix Composite Materials and their Laminates
- DIN EN 2563 (1997-03): Aerospace Series – Carbon Fibre Reinforced Plastics – Unidirectional Laminates – Determination of Apparent Interlaminar Shear Strength
- ISO 14130 (1997-12): Fibre-reinforced Plastic Composites – Determination of Apparent Interlaminar Shear Strength by Short-beam Method; Technical Corrigendum 1: 2003-11
- Altstädt, V.: Testing of Composite Materials. In: Grellmann, W., Seidler, S. (Eds.): Polymer Testing. Carl Hanser Munich (2022) 3rd Edition, 537–538 (ISBN 978-1-56990-806-8; ePub ISBN 978-1-56990-808-2; see AMK-Library under A 22)