ASTM D4812-19

5.1 The pendulum-impact test indicates the energy to break standard test specimens of specified size under stipulated conditions of specimen mounting and pendulum velocity at impact.

5.2 The energy lost by the pendulum during the breakage of the specimen is the sum of the energies required to produce the following results:

5.3 For relatively brittle materials for which fracture propagation energy is small in comparison with the fracture initiation energy, the indicated impact energy absorbed is, for all practical purposes, the sum of items given in 5.2.1 and 5.2.3. The toss correction (5.2.3) may represent a very large fraction of the total energy absorbed when testing relatively dense and brittle materials.

5.4 For materials for which the fracture propagation energy (5.2.2) may be large compared to the fracture initiation energy (5.2.1), factors (5.2.2, 5.2.5, and 5.2.9) can become quite significant, even when the specimen is accurately machined and positioned and the machine is in good condition with adequate capacity (Note 3). Bending (5.2.4) and indentation losses (5.2.8) may be appreciable when testing soft materials.

5.5 In a well-designed machine of sufficient rigidity and mass the losses due to the items given in 5.2.6 and 5.2.7 should be very small. Vibrational losses (5.2.6) can be quite large when specimens of tough materials are tested in machines of insufficient mass which are not securely fastened to a heavy base.

5.6 This test method requires that the type of failure for each specimen be recorded as one of the three coded categories defined as follows:

5.7 The value of this impact test method lies mainly in the areas of quality control and materials specification. The fact that a material shows twice the energy absorption of another under these conditions of test does not indicate that this same relationship will exist under another set of test conditions. The ranking of materials may even be changed under different testing conditions.

5.8 Before proceeding with this test method, reference should be made to the specification of the material being tested. Any test specimen preparation, conditioning, dimensions, or testing parameters, or combination thereof, covered in the material specification shall take precedence over those mentioned in this test method except in cases where to do so would conflict with the purpose for conducting testing. If there are no material specifications, then the default conditions apply.

1.1 This test method covers the determination of the resistance of plastics to breakage by flexural shock, as indicated by the energy extracted from standardized pendulum-type hammers, mounted in standardized machines, in breaking standard specimens with one pendulum swing. The result of this test method is reported as energy absorbed per unit of specimen width.

1.2 The values stated in SI units are to be regarded as standard. The values given in parentheses are for information only.

1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.