The Short Beam Shear Test for Composite Materials

  • 20th September 2019
  • Joe Carruthers
  • Reading time: about 3 minutes

The “short beam shear” test is a relatively quick, easy and inexpensive test to perform. This is due to the simplicity of its test fixtures and samples. It is typically used to compare or benchmark the performance of different materials for R&D or quality control purposes.

How is the Short Beam Shear Test Performed?

Different standards (e.g. ASTM D2344, BS EN ISO 14130:1998) describe slightly different versions of the short beam shear test. However, the underlying principles are the same. A specimen with a rectangular cross-section is placed upon two lower supports that are a fixed distance apart (the “span”). A central load is then applied to the specimen from above. The geometry of the specimen is such that its span-to-thickness ratio is relatively low. This ensures that the specimen is predominantly loaded in shear.

The output from the test is the load at which the specimen fails. From this, the “short beam strength” (ASTM D2344) or “apparent interlaminar shear stress” (BS EN ISO 14130:1998), S, can be calculated as follows:

What the Short Beam Shear Test Does (and Doesn’t) Tell Us

It is important to note that the stress state produced by this test does not satisfy a condition of pure shear. As such, specimen failures by modes other than shear are possible. For this reason, ASTM D2344 refers simply to the “short beam strength” of a specimen (i.e. with no mention of shear). BS EN ISO 14130:1998 takes a different approach by declaring any non-shear failure modes as “unacceptable” when reporting the results of tests.

It should, therefore, be clear that the short beam shear test is not measuring a fundamental material property of a composite in the same way that, for example, a tensile test is used to measure Young’s modulus (stiffness). Rather it is an indicator of the performance of a material under shear-like loading conditions. For this reason, the short beam shear test is best used to compare the relative performance of different materials. Or as a tool for quality control when benchmarking against an established threshold.

If the true shear properties of a composite are required (e.g. for design purposes) then more complex test methodologies are available. These include the Iosipescu shear test or the V-Notched Rail shear test.

At Coventive we use the short beam shear test alongside a wide range of other tests as part of our material characterisation services. If you have any enquiries regarding composite materials testing, please do not hesitate to contact us.

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About the author

Joe Carruthers

Joe is the Managing Director of Coventive Composites.

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