5.1 Test Method D3822 using test specimens having gauge lengths of 10 mm [0.4 in.] or greater is considered satisfactory for acceptance testing of commercial shipments since the test method has been used extensively in the trade for acceptance testing. Critical differences noted in Tables 1 and 2 were obtained on man-made fibers having a gauge length of 25 mm [1.0 in.] and 250 mm [10 in.]. Natural fibers or fibers having lesser or greater gauge lengths may provide different values and may require comparative testing. (See 5.1.1.)

5.1.1 In cases of a dispute arising from differences in reported test results when using Test Method D3822 for acceptance testing of commercial shipments, the purchaser and the supplier should conduct comparative tests to determine if there is a statistical bias between their laboratories. Competent statistical assistance is recommended for the investigation of bias. As a minimum, the two parties should take a group of test specimens which are as homogeneous as possible and which are from a lot of material of the type in question. The test specimens should then be randomly assigned in equal numbers to each laboratory for testing. The average results from the two laboratories should be compared using Student's t-test for unpaired data and an acceptable probability level chosen by the two parties before the testing begins. If a bias is found, either its cause must be found and corrected or the purchaser and the supplier must agree to interpret future test results for that material in view of test results with consideration to the known bias.

5.2 The breaking tenacity, calculated from the breaking force and the linear density, and the elongation are fundamental properties that are widely used to establish limitations on fiber processing or conversion and on their end-use applications. Initial modulus is a measure of the resistance of the fiber to extension at forces below the yield point. The tangent modulus and tensile stress at specified elongation may be used to differentiate between the probable performance of fibers in processing and end-use performance. The breaking toughness is an indication of the durability of materials produced from the fiber.

5.3 It is recognized that computerized results are used extensively in the industry. When comparing results from two laboratories using computerized tensile testers, the algorithms used to derive results must be examined for parity, that is, how the maximum slope and specimen failure or rupture are determined.

5.4 The breaking strength of wet fibers tested in air may be different from wet fibers tested while immersed.

5.4.1 Tests on wet specimens are usually made only on fibers which show a loss in breaking force when wet or when exposed to high humidity, for example, yarns made from animal fibers and man-made fibers based on regenerated and modified cellulose. Wet tests are made on flax fiber to detect adulteration by failure to show a gain in breaking force.

1.1 This test method covers the measurement of tensile properties of natural and man-made single textile fibers of sufficient length to permit mounting test specimens in a tensile testing machine.

1.2 This test method is also applicable to continuous (filament) and discontinuous (staple) fibers or filaments taken from yarns or tow. When the fibers to be tested contain crimp, or if the tow or yarns have been subjected to bulking, crimping, or texturing process, the tensile properties are determined after removal of the crimp.

1.3 The words “fiber” and “filament” are used interchangeably throughout this test method.

1.4 This test method is also applicable to fibers removed from yarns, or from yarns processed further into fabrics. It should be recognized that yarn and manufacturing processes can influence or modify the tensile properties of fibers. Consequently, tensile properties determined on fibers taken from yarns, or from yarns that have been processed into fabrics, may be different than for the same fibers prior to being subjected to yarn or fabric manufacturing processes.

1.5 This test method provides directions for measuring the breaking force and elongation at break of single textile fibers and for calculating breaking tenacity, initial modulus, chord modulus, tangent modulus, tensile stress at specified elongation, and breaking toughness.

1.6 Procedures for measuring the tensile properties of both conditioned and wet single fibers are included. The test method is applicable to testing under a wide range of conditions.

1.7 As the length of the test specimen decreases, the tensile strength is likely to increase, but the accuracy of the tensile properties determined may decrease, which may require the need to increase the number of test specimens. This is particularly true for those properties dependent on the measurement of elongation, since the shorter lengths increase the relative effect of slippage and stretching of the test specimens within the jaws of either clamp.

1.8 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.

1.9 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 and health practices and determine the applicability of regulatory limitations prior to use.