【国外标准】 Standard Test Method for Compressive Residual Strength Properties of Damaged Sandwich Composite Panels

5.1 Susceptibility to damage from concentrated out-of-plane forces is one of the major design concerns of many structures made of sandwich constructions. Knowledge of the damage resistance and residual strength properties of a sandwich construction is useful for product development and material selection.5.2 The residual strength data obtained using this test method is most commonly used in material selection, research and development activities, and establishing design allowables.5.3 The properties obtained using this test method can provide guidance in regard to the anticipated residual strength capability of sandwich constructions of similar facesheet and core material, adhesive, facesheet and core thickness, facesheet stacking sequence, and so forth. However, it must be understood that the residual strength of sandwich constructions is highly dependent upon several factors including geometry, thickness, stiffness, support conditions, and so forth. Significant differences in the relationships between the damage state and the residual compressive strength can result due to differences in these parameters.5.4 The compression strength from this test may not be equivalent to the compression strength of sandwich structures subjected to flexural compression testing.5.5 The reporting section requires items that tend to influence residual 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, specimen preparation, specimen conditioning, environment of testing, type, size and location of damage (including method of non-destructive inspection), specimen/fixture alignment and gripping, time at temperature, and speed of testing.5.6 Results from the residual strength assessment include the following: normalized compressive residual strength NCAI, compressive force as a function of crosshead displacement, and far-field surface strains as functions of crosshead displacement.1.1 This test method covers compression residual strength properties of sandwich constructions that have been subjected to quasi-static indentation or drop-weight impact per Practice D7766/D7766M.NOTE 1: When used to determine the residual strength of drop-weight impacted plates, this test method is commonly referred to as the Sandwich Compression After Impact test method.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, previously subjected to a damaging event, 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, the type, size, and location of damage 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 undamaged specimens, but care should be taken to prevent undesirable failure modes such as end crushing. Test Methods C364 and D7249/D7249M are the recommended test methods for undamaged sandwich panel compression strength by edgewise compression 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.