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V-notched shear tests

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  • Industry brochure: Composites PDF 7 MB

Purpose of the test

This test arrangement is used to determine both in-plane and interlaminar shear characteristics. Theoretically, each of the six possible shear planes can be tested separately. However, laminate manufacturing for measuring interlaminar shear strength characteristics is time consuming and therefore is typically not used.

The methods can be used for unidirectional composites and multidirectional 0°/90° fabrics and textiles. Laminates with 45° orientation cannot be measured using this method, since the normal stress with 45° orientation would be very high and would falsify results.

Through the notch, a concentration of shear stress arises under deformation of the specimen, which ultimately leads to a break. Strain gauges are placed at ±45° in the direction of the shear plane in order to determine the shear extension. Two variations of the method have been standardized:

  • Iosipescu method to ASTM D5379 and
  • V-notched rail shear method to ASTM D7078

There are also other methods used to characterize in-plane shear properties.

Iosipescu method to ASTM D5379

  • Since the specimen is relatively small, this method is particularly suited for measuring unidirectional and 0°/90° fibers with a rather fine fiber structure.
  • The test tool consists of one fixed clamping mechanism and one clamping mechanism guided in the axial direction. It is used by the testing machine to introduce deformation. A zone of torque-free shear load emerges between the notches when a compression load is applied.
  • The results are shear behavior, 0.2% shear stress, maximum shear stress, and the secant shear modulus.

V-notched rail shear method – ASTM D7078

  • Specimens used in the v-notched rail shear test are larger than those used in the Iosipescu method, meaning the method is suitable for measuring laminates with larger webbing.
  • The shear deformation is introduced by the two parts of the tool, which are moved in the tensile direction during measurement. The arrangement specified by the standard does not include direct guiding as is used in the Iosipescu method.
  • The tool must be precisely aligned using the adjustment gauges prior to the test.
  • The results are shear behavior, 0.2% shear stress, maximum shear stress, and the secant shear modulus.

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