4.1 This test method determines the cleavage force required to peel stiff facings from the core of sandwich panels, and is used to determine how well the facing is bonded to the core. Test Method D1781 only works well with flexible facings. As a guideline, the cleavage test method would work better on sandwich panels that have facings with a bending stiffness (EI) of greater than approximately 27.3 lb-in²/inch width (3.09 kN·mm ²/mm width). This converts to approximately 0.032 in. (0.81 mm) 6061 T6 aluminum alloy, 0.023 in. (0.57 mm) steel, and 0.046 in. (1.18 mm) fiberglass facings.

1.1 This test method covers the determination of the cleavage force to peel stiff facings from sandwich panels.

1.2 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.

1.3 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.

1.4 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.