Standard Test Method for Shear Strength

Micrometers and Calipers

• A micrometer with a 4 to 7 mm [ 0.16 to 0.28 in.] nominal diameter ball-interface(pictured first)/anvil interface(pictured second) is used to measure the thickness of the material.

• A ball interface is recommended when measuring the thickness of irregular surfaces (e.g. when a surface is neither smooth nor flat).

• A flat anvil interface of a micrometer or caliper (pictured at the bottom) is recommended when the surfaces of the material are smooth.

• A flat anvil surface caliper/micrometer will be used to measure the length and width.

• For typical material dimensions, an instrument with an accuracy of +/- 0.025mm [ +/- 0.001 in.] is enough for our needs.

Loading Fixtures

• The loading will be either a 3-point or 4-point configuration, 3-point meaning one downward force applied and 4-point meaning two downward forces applied (both pictured first).

• The material being tested will be held by two support bars located below the material.

• The standard loading fixture will be a 3-point configuration and the support bars will be separated by a distance of 150mm [6.0 in.].

• The support bars will be designed so the specimen has a free rotation at the loading and support points. These bars should also have sufficient stiffness to avoid deflection under load.

• The recommended configuration for loading blocks is 25mm [1.0 in.] wide flat steel blocks that will contact the specimen through rubber pressure pads.

• The loading block will be used either with a cylindrical pivot or a V-shaped bar riding in a V-groove (I don’t know if this information is relevant)

Testing Machine

• The machine should have both a stationary head and a movable head.

• For the drive mechanism, it should be able to give a controlled velocity to the movable head with respect to the stationary head. The movable head shall be capable of producing failure within 3 to 6 minutes, the standard speed for crosshead displacement is 6mm/min [0.25 in./min]

• The machine should also be capable of indicating the total force being carried by the test specimen.

Conditioning Chamber

• Outside of lab environments, you must control the temperature and vapour-levels for the conditioning of materials, temperatures must be kept within +/- 3 degrees celsius and have a relative humidity level of +/- 3%.

Environmental Test Chamber

• An environmental test chamber must be used if not testing in ambient lab environments. The chamber must be able to maintain the gage section of the test specimen during the test.