ASTM D 8637/D8637M : 2025

1.1This test method describes the determination of the Mode I dominant fracture toughness, G_Ic, associated with face sheet-to-core separation of sandwich constructions using the single cantilever beam (SCB) specimen. This separation can consist of a disbond of the face sheet-to-core interface or a fracture of the core near the face sheet-to-core interface region.

1.2This test method is limited to use with sandwich constructions with face sheets consisting of continuous-fiber or discontinuous-fiber (tape, fabric, or both) reinforced composites in which the laminate is balanced with respect to the test direction. Permissible core material forms include those with continuous bonding surfaces, such as balsa wood and foams, as well as those with discontinuous bonding surfaces, such as honeycomb. This test method may prove useful for other types and classes of sandwich constructions; however, certain interferences have been noted (see 6.8).

1.3The measured fracture toughness of the face sheet-to-core interface region is a Mode I dominant structural property that is a function of the dimensions and constituent materials of the sandwich construction and the method of manufacturing.

1.4Certain face sheet/core combinations may cause fracture loading conditions that deviate from a Mode I dominant condition, resulting in a fracture mode not addressed by this standard. Therefore, only combinations of face sheet and core materials that yield Mode I dominant fracture loading conditions in the SCB specimen are permissible. Further details are provided in 6.7. Mode I dominant fracture in the SCB specimen is defined as having a Mode-I component of energy release rate (ERR) equal to at least 90 % of the total ERR.

1.5The values stated in 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, and values from the two systems shall not be combined.

1.6This 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.

1.7This 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.