V-NOTCHED BEAM SHEAR FIXTURE (IOSIPESCU SHEAR)
The primary design characteristic of the ASTM D5379 test fixture is to ensure that the applied test load line effectively passes through the root of the V-notch. Any failures in positioning the specimen will cause off-axis forces to effect non-shear loads into the specimen. This is accomplished through the use of a notch alignment pin that can be raised to set the specimen position while it is being assembled. The shear forces are then maintained by using a nearly frictionless cross-roller bearing, which ensures movement is vertical and only in the load direction. All other axes are rigidly constrained, including the out-of-plane Y rotation seen in linear bush-based designs.
ASTM D 5379 Specimen Dimensions
According to the ASTM D 5379 test standard, the sample thickness can be selected over a wide range. However, as long as possible, the thickness should be kept in the 3-4 mm range.
Testing of materials with a thickness of less than 2.5 mm [0.100 inches] should be performed using tabs.
Application Range for ASTM D 5379
ASTM D5379 shear characteristics of fiber-reinforced composites the application range is planned to include the following laminate forms:
• unidirectional laminates with fiber directions of 0° or 90°
• unidirectional laminates with the same number of plies in the 0° and 90° fiber directions
• fabric laminates with a warp direction of 0° or 90°
• plastics reinforced with short, randomly distributed fibers
1. Prepare V-notched beams according to ASTM D 5379 testing standard.
2. Attach the strain gauges to the test controller and place them at +45 and -45 degrees to the test specimen's loading axis. Zero the force measurement before starting to test.
3. Insert the sample loosely into the ASTM D 5379 (IOSIPESCU SHEAR), ensuring that the notch alignment tool is pulled into the notch. Squeeze the left chin-side-jaw gently, followed by the right chin. While continuing to support the rear, ensure that the specimen is centered in the fixture and touches both the upper and lower grasp jaws on both sides.
4. Apply consistent strain rate force till specimen failure. Keep track of the force against tension (or position). Record the maximum force, force at break, and strain as the specimen breaks.
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