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ASTM D3518 | Composites | Tension Testing

ASTM D3518 is a testing standard designed to measure the in-plane shear response of polymer matrix composite materials reinforced by high-modulus fibers. A uniaxial test of ±45˚ laminate is performed with strain instrumentation in both longitudinal and transverse directions and continuous load-strain data recording. The calculations that can be derived include shear stress and strain, shear modulus of elasticity and offset shear strength for a ±45˚ laminate. The in-plane shear stress is directly calculated from the applied axial load and the related shear stress is derived from the strain data obtained by extensometers or other strain measurement devices. Before conducting ASTM D3518, it is important to read the entire specification in the relevant ASTM publication.

ASTM D3518 | Composites | Tension Testing

  1. Prepare test specimen from the ±45˚ laminate with constant rectangular cross sections in accordance with the Test Method D3039.
  2. Place the specimen in the fixture by centering it between the grip interfaces. Make sure that the entire grip length contacts the grip faces when the fixture is closed.
  3. Attach the required strain gauges or extensometers to the mid-span, mid-width location of the specimen.
  4. Apply the load at a constant rate until failure. 5% calculated shear strain should be considered the maximum possible shear stress. If failure doesn’t occur within the 5% shear strain, truncate the test data to the 5% shear strain mark.
Calculations:
  • Shear Stress/Maximum Shear Stress
  • Shear Strain/Maximum Shear Strain
  • Shear Modulus of Elasticity
  • Offset Shear Strength

ASTM D3518 | Composites | Tension Testing

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