Short Beam Shear (ASTM D 2344)

The Short Beam Shear test (SBS) described in DIN EN 2563 /2377, DIN EN ISO 14130 and ASTM D 2344 for the determination of apparent interlaminar shear strength is a modified 3-Point flexural test. The span length of the fixture is small as compared to the specimen’s thickness which induces shear stress to the specimen. The geometry of the specimen is a short beam of thermoplastics or thermosettings continuously reinforced by fibres in 0° or 0°/90°-direction. The norm defines apparent interlaminar shear strength as “maximum shear stress calculated at half thickness of specimen at the moment of first failure.”[1]

The norm also quotes limits of this method:

  • Depending on the material configuration, “the results can be influenced by interfering strain/flexural stresses or flexural/torsion moments etc.” [2]
  • The specimen may possibly fail due to flexural or plastic deformation, which makes it impossible to determin the real shear stress at the moment of failure.
  • The method may not be used to determin characteristic values for construction purposes. It may only be used for material selection or quality check.
  • The results are no quantitative (absolute) values. They may only be used for comparison within one test series.
On the other hand, the SBS testing method works with only very small and geometrically simple specimen. Using a small amount of material, qualitative information about the resin-fibre relation can be obtained.

[1]: DIN EN 2563, “Aerospace series, Carbon fibre reinforced plastics, Unidirectional laminates, Determination of the apparent interlaminar shear strength”, CEN, 1996
[2]: DIN ISO 14130, “Fibre reinforced plastic composites, Determination of apparent interlaminar shear strength using short-beam method”, CEN, 1997