ASTM D5379 Iosipescu Fixture V-Notch Shear is for Strength Composite Material, is a four-point asymmetric flexure fixture which tests for shear properties by means of the V-notched beam method. Each half of the fixture contains a wedge-action grip which lightly clamps one half of the test specimen across the specimen width while simultaneously supporting the specimen on its back face. One of the grips, normally the lower half, is mounted on a base plate which also supports a linear bearing shaft, while the other grip, normally in the upper position, contains a linear bearing which mounts over the shaft on the base. Each element is attached to or supported by one of the testing machine heads. A specified gap is left unsupported between fixture halves. An alignment tool is provided to ensure that the specimen notch is aligned with the line of action of the loading fixture. Reference ASTM Standard D 5379 

Testing to ASTM D5379:

The Iosipescu shearing device is guided in the longitudinal direction. It is placed on a compression platen or the crosshead of the testing system.

A specimen notched on both sides is inserted in the shear test fixture. A zone of torque-free shear load emerges between the notches when a compression load is applied. The fibers must lie parallel or transverse in relation to the load direction. The shear strain is measured via two strain gauges that are applied at a 45° angle to the shear plane.

Characteristic values determined according to ASTM D5379:

Shear behavior

0.2% shear stress

Max. shear stress

Secant shear module

ASTM D5379/D5379M-19 

Standard Test Method for Shear Properties of Composite Materials by the V-Notched Beam Method