Iosipescu Shear Test Fixture
Standard Test Method for Shear Properties of Composite Materials by the V-Notched Beam Method
ASTM D5379 describes a shear test for compostie materials such as carbon fiber, ceramics, and certain types of advanced metallurgies. This test is one of the oldest shear tests for composites and was developed and adopted during the 1980's. Since then, the ASTM D7078 V-Notched Rail Shear Test has gained popularity and is also in widespread use. Both procedures are used to test the same criteria, however D7078 should be used when there is a risk of edge crushing on the specimen's loading face.
A small V-notched specimen is sheared perpendicular to the normal plane. The test is performed at a controlled rate of speed using a compression testing machine.
The sample is about 3 inches long and has a V notch along the center on both the top and the bottom which is cut at a 45 degree angle. This type of geometry isolates the area where the shear stress is focused.
This test requires an Iosipescu shear fixture which is specifically designed for use with a Universal Testing Machine. UGC offers a complete line of shear fixtures for ASTM testing.
Specific calculations can be made based on the exact size of the cross-sectional area that experiences the shear stress. Shear strength is usually given by the peak load seen during the test divided by the area of the shearing zone. Along with shear strength, there are a few additional calculations which are laid out in the official ASTM publication. Strain guages can be mounted directly onto the sample to measure localized strain deformation.