ASTM-D624:00(R2020) pdf free download – Standard Test Method for Tear Strength of Conventional Vulcanized Rubber and Thermoplastic Elastomers.
4.2.2 Type B. a razor-nicked test piece with a crescent shape and with tab ends, as shown in Fig. 1, Die B. The force in this test piece acts in a direction substantially along the major axis (length) and perpendicular to the “nick”, or razor cut. Type B also measures tear propagation and is preferred over Type A when the test sample allows.
4.2.3 Type C, an un-nicked test piece with a 900 angle on one side and with tab ends, as shown in Fig. 1, Die C. The force acts on the test piece in a direction substantially parallel to the tab ends of the specimen (45° to the 90° center angle) in the direction of grip separation. Type C measures rupture, or tear initiation strength at the stress concentration located at the 90° apex. If tear initiation does not occur at the apex, the results are more indicative of tensile strength than tear strength.
4.2.4 Type T, a trouser tear test piece. as shown in Fig. 2. Type T measures tear propagation in a direction parallel to the length of both legs.
4.2.5 Type CP, a test piece described in Fig. 3, which is a modified trouser tear test piece with a constrained path for the Lear. Type CP also measures tear propagation in a direction parallel to the length of both legs, hut the constrained path prevents the tear from propagating away from this path. and the thicker legs eliminate the influence of leg extension which may occur with Type T test pieces. See (1) for more information on CP tear testing.
4.3 No Correlation of results from one test type to another should be expected, as each test type measures tear strength for a different tear specimen geometry.
5. Significance and Use
5.1 Vulcanized rubber and thermoplastic elastomers (TPE) often fail in service due to the generation and propagation of a special type of rupture called a tear. This test method measures the resistance to tearing action.
5.2 Tear strength may be influenced to a large degree by stress-induced anisotropy (mechanical tIhering), stress distribution, strain rate, and test piece size. The results obtained in a tear strength test can only he regarded as a measure under the conditions of that particular test and may not have any direct relation to service performance. The significance of tear testing must be determined on an individual application or product performance basis.
6. Apparatus
6.1 Testing Machine—The testing machine shall conform to the requirements as specified in Test Methods D4 12. Ii shall be capable of registering the applied forces within ± 2 % of the total force range or capacity during the test while maintaining the specified rate of jaw separation:
6.1.1 For Type A. B or C test pieces. the rate of jaw separation shall be 500 ± 50 mm/mm. (20 ± 2.0 in./min.).
6.1.2 For Type T and Type CP test pieces, the rate of jaw separation shall be 50 ± 5 mm/mm. (2 ± 0.2 in./min.).