ASTM D4812-11
Standard Test Method for Unnotched Cantilever Beam Impact Resistance of Plastics

Standard No.

ASTM D4812-11

Release Date

2011

Published By

American Society for Testing and Materials (ASTM)

Status

Be replaced

Replace By

ASTM D4812-19

Latest

ASTM D4812-19e1

Scope

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.

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

To initiate fracture of the specimen,

To propagate the fracture across the specimen,

To throw the free end (or pieces) of the broken specimen (toss correction),

To bend the specimen,

To produce vibration in the pendulum arm,

To produce vibration or horizontal movement of the machine frame or base,

To overcome friction in the pendulum bearing and in the indicating mechanism, and to overcome windage (pendulum air drag),

To indent or deform plastically the specimen at the line of impact, and

To overcome the friction caused by the rubbing of the striking nose (or other part of the pendulum) over the face of the bent specimen.

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.

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.

Note 38212;Although the frame and base of the machine should be sufficiently rigid and massive to handle the energies of tough specimens without motion or excessive vibration, the pendulum arm cannot be made very massive because the greater part of its mass must be concentrated near its center of percussion at the striking nose. Locating the striking nose precisely at the center of percussion reduces vibration of the pendulum arm when used with brittle specimens. However, some losses due to pendulum-arm vibration, the amount varying with the design of the pendulum, will occur with tough specimens even when the striking nose is properly positioned.

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.

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

C (Complete Break)A break in which the specimen is separated into two or more pieces.

P (Partial Break)An incomplete break that has fractured at least 90 % of the depth of the specimen.

NB (Non-Break)An incomplete break where the fracture extends less than 90 % of the depth of the specimen.

For tough materials the pendulum may not have the energy necessary to completely break the extreme outermost fibers and toss the broken piece or pieces. Results obtained from “non-break” specimens shall be considered a departure from standard and shall be reported as “NB” only and a numerical value shall not be reported. Impact values cannot be directly compared for any two mater...........

ASTM D4812-11 history

• 2019 ASTM D4812-19e1 Standard Test Method for Unnotched Cantilever Beam Impact Resistance of Plastics
• 2019 ASTM D4812-19 Standard Test Method for Unnotched Cantilever Beam Impact Resistance of Plastics
• 2011 ASTM D4812-11 Standard Test Method for Unnotched Cantilever Beam Impact Resistance of Plastics
• 2006 ASTM D4812-06 Standard Test Method for Unnotched Cantilever Beam Impact Resistance of Plastics
• 2005 ASTM D4812-05 Standard Test Method for Unnotched Cantilever Beam Impact Strength of Plastics
• 1999 ASTM D4812-99 Standard Test Method for Unnotched Cantilever Beam Impact Strength of Plastics