Significance and Use
5.1 This test method provides a standard method of determining the open-hole (notched) strength of the sandwich panel for structural design allowables, material specifications, and research and development.
5.2 The reporting section requires items that tend to influence notched sandwich compressive strength to be reported; these include the following: facesheet and core materials, core density, cell size and wall thickness if applicable, film adhesive, methods of material fabrication, accuracy of lay-up orientation, facesheet stacking sequence and thickness, core thickness, overall specimen thickness, specimen geometry (including hole diameter, diameter-to-thickness ratio, and width-to-diameter ratio), specimen preparation (especially of the hole), specimen conditioning, environment of testing, type, specimen/fixture alignment, time at temperature, and speed of testing. Further, notched sandwich compressive strength may be different between precured/bonded and co-cured facesheets of the same material.
5.3 The compression strength from this test may not be equivalent to the compression strength of sandwich structures subjected to flexural compression testing.
Scope
1.1 This test method determines the open-hole compressive strength of sandwich constructions in a direction parallel to the sandwich facesheet plane. 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).
1.2 Several important test specimen parameters (for example, facesheet thickness, core thickness, and core density) are not mandated by this test method; however, repeatable results require that these parameters be specified and reported.
1.3 The method utilizes a flat, rectangular specimen, with a centrally located open through-hole, which is tested under edgewise compressive loading using a stabilization fixture.
1.4 The properties generated by this test method are highly dependent upon several factors, which include: specimen geometry, sandwich component materials and dimensions (facesheet, core, and adhesive), methods of fabrication, and boundary conditions. Thus, results are generally not scalable to other sandwich constructions, and are particular to the combination of geometric and physical conditions tested.
1.5 This test method can be used to test unnotched specimens, but care should be taken to prevent undesirable failure modes such as end crushing. ASTM Test Methods C364 or D7249/D7249M are the recommended test methods for unnotched sandwich panel compression strength or long beam flexure, respectively.
1.6 Units—The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used independently of the other, and values from the two systems shall not be combined.
1.6.1 Within the text, the inch-pound units are shown in brackets.
1.7 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.
1.8 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.
