5.1 In general, these procedures are more suitable for testing woven fabrics than knit fabrics.

5.2 Both test options in this test method are considered satisfactory for acceptance testing of commercial shipments since current estimates of between-laboratory precision are acceptable and the method is used extensively in the trade for acceptance testing.

5.2.1 In case of a dispute arising from differences in reported test results when using this test method 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 that are as homogeneous as possible and that are from a lot of material of the type in question. 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 the appropriate statistical analysis and an acceptable probability level chosen by the two parties before testing is begun. 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 with consideration to the known bias.

5.3 The stiffness of a fabric may change with storage.

5.4 No evidence has been found showing that bending length is dependent on the width of the test specimen. The tendency for specimens to curl or twist will affect the result, because of the rigidity provided at the edge of the specimen. Consequently, the wider the strip, the less important is the edge effect. For fabrics having only a slight tendency to curl, a 2.5 cm wide strip has been found to be satisfactory. As the tendency to curl increases, this width may be increased (see Note 10).

5.5 This method differs from Test Method F3260 which requires tracking of sample surface orientation, and is used to evaluate absorbable and partially absorbable medical textiles.

1.1 This test method covers the measurement of stiffness properties of fabrics. Bending length is measured and flexural rigidity is calculated. Two procedures are provided.

1.1.1 Option A—Cantilever Test, employing the principle of cantilever bending of the fabric under its own mass.

1.1.2 Option B—Heart Loop Test, employing the principle of a loop formed in a fabric strip and hung vertically.

1.2 This test method applies to most fabrics including woven fabrics, air bag fabrics, blankets, napped fabrics, knitted fabrics, layered fabrics, pile fabrics. The fabrics may be untreated, heavily sized, coated, resin-treated, or otherwise treated.

1.2.1 This method may be used to determine the stiffness of nonwoven materials (for example, hydroentangled, dry laid, needlepunch, resin bonded, thermal, and wet laid) or refer to Test Method D5732. To determine the stiffness of medical textiles (for example, surgical mesh, films, and membranes), refer to Test Method F3260.

Note 1: The formula to calculate flexural rigidity in D5732-95 (2001) is incorrect and should not be used. Utilize the formula presented in 11.5 of Test Method D1388.

1.3 Units—The values stated in SI units are to be regarded as the standard. The values given in parentheses after SI units are provided for information only and are not considered standard.

1.4 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.

1.5 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.