Specialized shear fixture on an eXpert 2600 for ASTM D5961
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ASTM D5961 | Composites | Shear Testing

ASTM D5961 is a testing specification that determines the bearing response of pinned or fastened joints using multi-directional polymer matrix composite laminates reinforced by high-modulus fibers. The bearing force is created by tension or compression loading. It can be applied through a lightly torqued fastener (or pin) that is reacted in single shear or double shear depending on the test procedure. There are four different procedures to calculate the bearing response:

  • Procedure A: Double Shear Tensile Loading
  • Procedure B: Single Shear Tensile or Compressive Loading of a Two-Piece Specimen
  • Procedure C: Single Shear Tensile Loading of a One-Piece Specimen
  • Procedure D: Double Shear Compressive Loading

The calculations that can be derived include bearing stress/strength, bearing strain, bearing chord stiffness, offset bearing strength and ultimate bearing strain, initial peak bearing strength. Results from each procedure should not generally be expected to yield comparable results due to difference in the loading direction, localized damage modes, support fixture friction and specimen dimension differences. Before conducting ASTM D5961, it is important to read the entire specification in the relevant ASTM publication.

ASTM D5961 | Composites | Shear Testing

Test Procedure A – Double Shear Tensile Loading

  1. Prepare a 135 mm (5.3 in) long, 36 mm (1.4 in) wide and 3-5mm (0.1 in – 0.2 in) thick rectangular specimen specified by the standard. The specimen should have a centerline hole, 18mm (0.7 in) away from the edge, with a 6 mm (0.2 in) diameter. It is important to maintain the specimen width to hole diameter at 6, even if the specimen dimensions change.
  2. Insert the specimen into the fixture loading plate. The fixture should allow a bearing strain indicator to monitor the hole deformation as indicated in the standard. Transducers used should meet minimum Class-B2 requirements. Transducer and gauge length locations can be found in the ASTM publication.
  3. Apply bearing load in tension, through a close-tolerance lightly torqued single fastener (or pin) that is reacted in double shear. Monitor the applied force and the deformation of the hole.
  4. Stop the test when the maximum force is reached. The maximum force reached should be noted as the ultimate bearing strength.
  5. Plot the bearing stress versus the bearing strain for the entire test, note the failure mode.

Test Procedure B – Single Shear Tensile or Compressive Loading of a Two-Piece Specimen

  1. Prepare rectangular test specimen composed of two like halves fastened together through one or two centerline holes at the end of each half. Single or double fastener options are available and dimensions below are for the single fastener option.
  2. Select either Unstabilized or Stabilized Configuration
    1. Unstabilized:
      1. Unstabilized configuration is only intended for tensile loading. If no support fixture will be used, the dimensions of the single-fastener specimen should be 135 mm (5.3 in) long, 36 mm (1.4 in) wide and 3-5mm (0.1 in – 0.2 in) thick as specified by the standard. The specimen should have a 6 mm (0.2 in) diameter hole, 18mm (0.7 in) away from the edge. The doubler, which is used to minimize the eccentricity of the applied load, should be made from the same laminate as the specimen and should be 75 mm (3 in) long. The ends of the test specimen should be gripped in the grip jaws. Mount the transducer on the specimen as specified in the standard.
    2. Stabilized:
      1. If compressive loading is applied, then a support fixture should be used to stabilize the specimen. Then, the length of the single-fastener specimen should be 189 mm (7.4 in) and the doubler length should be 129 mm (5.1 in). All the other dimensions should be the same as above. The stabilized configuration allows tensile or compressive loading. The test specimen halves are clamped in hydraulic wedge grips and the force is sheared into the support fixture, then to the specimen. Mount the transducer on the specimen as specified in the standard.  For the double-fastener specimen, extend the length of each specimen half by the required distance and place a second bearing hole in line with the first hole. Please refer to the ASTM standard for the dimensions of the double fastener specimen.
  3. Apply bearing load, monitor the applied force and the deformation of the hole(s).
  4. Stop the test when the maximum force is reached. The maximum force reached should be noted as the ultimate bearing strength.
  5. Plot the bearing stress versus the bearing strain for the entire test, note the failure mode.

Test Procedure C – Single Shear Tensile Loading of a One-Piece Specimen

  1. Prepare a rectangular sample as specified in Procedure A.
  2. Insert the specimen into the fixture loading plate. The fixture should allow a bearing strain indicator to monitor the hole deformation as indicated in the standard. Transducers used should meet minimum Class-B2 requirements. Transducer and gauge length locations can be found in the ASTM publication.
  3. Apply bearing load in tension, through a close-tolerance lightly torqued fastener that is reacted in single shear, monitor the applied force and the deformation of the hole.
  4. Stop the test when the maximum force is reached. The maximum force reached should be noted as the ultimate bearing strength.
  5. Plot the bearing stress versus the bearing strain for the entire test, note the failure mode.

Test Procedure D – Double Shear Compressive Loading

  1. Prepare a rectangular sample as specified in Procedure A.
  2. Insert the specimen into the fixture loading plate. The fixture should allow a bearing strain indicator to monitor the hole deformation as indicated in the standard. Transducers used should meet minimum Class-B2 requirements. Transducer and gauge length locations can be found in the ASTM publication.
  3. Apply bearing load in compression, through a close-tolerance lightly torqued fastener that is reacted in double shear, monitor the applied force and the deformation of the hole.
  4. Stop the test when the maximum force is reached. The maximum force reached should be noted as the ultimate bearing strength.
  5. Plot the bearing stress versus the bearing strain for the entire test, note the failure mode.
Calculations:
  • Width to Diameter Ratio
  • Bearing Stress/Strength
  • Bearing Strain
  • Bearing Chord Stiffness
  • Determination of Effective Origin
  • Ultimate Bearing Strain
  • Offset Bearing Strain

ASTM D5961 | Composites | Shear Testing

ASTM D5961Recommended Equipment
Testing System
Fixturing
  • ASTM D5961 Fixture
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