ASTM D256:2006 pdf free download – Standard Test Methods for Determining the lzod Pendulum Impact Resistance of Plastics.
5.9 The value of the impact methods lies mainly in the areas of quality control and materials specification. If two groups of specimens of supposedly the same material show significantly different energy ahsorptions, types of breaks, critical widths, or critical temperatures. it may be assumed that they were made of differcnt materials or were exposed to different processing or conditioning environments. 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 order of toughness may even be reversed under different testing conditions.
NOTE 8—A documerned discrepancy exists between manual and digital impact testers, primarily with thermoset materials, including phenolics. having an impact value of less than 54 J/m [I ft-lb/in.]. Comparing data on the same material, tested Ofl both manual and digital impact testers. may show the data from the digital tester to be significantly lower than data from a manual tester. In such cases a correlation study may be necessary to properly define the true relationship between the instruments.
TEST METHOD A—CANTILEVER BEAM TEST
6. Apparatus
6. 1 The machine shall consist of a massive base on which is mounted a vise for holding the specimen and to which is connected, through a rigid frame and bearings, a pendulum- type hammer. (See 6.2.) The machine must also have a pendulum holding and releasing mechanism and a mechanism for indicating the breaking energy of the specimen.
6.2 Ajig for positioning the specimen in the vise and graphs or tables to aid in the calculation of the correction for friction and windage also should be included. One type of machine is shown in Fig. 3. One design of specimen-positioning jig is illustrated in Fig. 4. Detailed requirements are given in subsequent paragraphs. General test methods for checking and calibrating the machine are given in Appendix X2. Additional instructions for adjusting a particular machine should be supplied by the manufacturer.
6.3 The pendulum shall consist of a single or multi— membered arm with a hearing on one end and a head, containing the striker, on the other. The arm must he sulliciently rigid to maintain the proper clearances and geometric relationships between the machine parts and the specimen and to minimize vibrational energy losses that are always included in the measured impact resistance. Both simple and compound pendulum designs may comply with this test method.
6.4 The striker of the pendulum shall be hardened steel and shall be a cylindrical surface having a radius of curvature of 0.80 ± 0.20 mm [0.031 ± 0.008 in.] with its axis horizontal pen and perpendicular to the plane of swing of the pendulum. The ami line of contact of the striker shall be located at the center of equ percussion of the pendulum within ±2.54 mm [±0.100 in.]
(See Note 9.) Those portions of the pendulum adjacent to the cylindrical striking edge shall be recessed or inclined at a suitable angle so that there will he no chance for other than this wl cylindrical surface coming in contact with the specimen during L the break.