ASTM D 747 Cantilever Beam Test

Scope:

This ASTM D 747 Standard test method describes slight deflections and purely elastic responses. Real-world conditions involve both elastic and plastic deformation. This method doesn’t differentiate them, yielding an apparent bending modulus. The preferred option is the tangent modulus from Test Methods D790, if feasible.

Test Procedure:

This ASTM D 747 Standard test method determines the Position of the test apparatus on a nearly level surface. Add the required weights to the pendulum. Adjust the load scale to zero if needed. Set the bending pin or plate to the appropriate span. Start the motor and maintain continuous operation throughout the tests to minimize friction in the weighing system. For optimal precision, select M so that, at a 3° angle, the load scale reads between 5 and 10. If this value is unknown, establish it through trial and error using the standard procedure.

Once M is determined, test five specimens. Ensure that one end of the specimen is inserted at least 3/4 of the way into the vise for a secure and even grip. Securely fasten the test specimen in the vise, aligning the centerline roughly parallel to the dial plate’s face. Apply an adequate load to the specimen by turning the hand crank to display a 1% load reading. Then, reset the angle pointer to zero and record and plot this point as part of the data. While holding down the motor engaging lever, take successive load scale readings at 3, 6, 9, 12, and 15° angles. Do not retest any specimens.

Video 01: Bending Test On a Cantilever Beam

Test Specimen:

As long as the material does not extend above the anvil’s width, the specimen width required per ASTM D 747 is between 5.0 and 25.4 mm (0.20 and 1.00 in.). To the nearest 0.025 mm (0.001 in. ), width must be measured.

Data:

This ASTM D 747 Standard test method calculates the apparent bending modulus,

Eb = 4swd3Mload scale reading100φ

where:

Pa (or psi), Eb = apparent bending modulus

S = span length, length from the pendulum weighing system’s center of rotation and the specimen vise to the contacting edge of the bending plate, m (or in),
w = specimen width, m (or in),
d = specimen depth, m (or in), and
M = total bending moment value of the pendulum system, Nm (or lbf-in), based on the moment

Conclusion:

In this test method, the Apparent Bending Modulus of Plastics using a Cantilever Beam. we can evaluate the procedures given in this method and Calculate the apparent bending modulus.