1.1 本试验方法包括测定承受弯曲的扁平夹层结构的面板特性，弯曲方式应确保施加的力矩产生夹层面板平面的曲率，并在面板中产生压缩力和拉力。允许的芯材形式包括具有连续粘合表面的芯材（如软木和泡沫）以及具有不连续粘合表面的芯材（如蜂窝）。 1.2 单位- 以国际单位制或英寸表示的数值- 磅单位应单独视为标准单位。每个系统中规定的值不一定是精确的等价物；因此，为确保符合本标准，每个系统应独立使用，且两个系统的值不得组合。 1.2.1 在文本中，英寸-磅单位显示在括号中。 1.3 本标准并非旨在解决与其使用相关的所有安全问题（如有）。本标准的用户有责任在使用前制定适当的安全、健康和环境实践，并确定监管限制的适用性。 注1: 测定夹层梁结构中单向聚合物基复合材料抗压强度的替代程序可在试验方法中找到 D5467/D5467M . 1.4 本国际标准是根据世界贸易组织技术性贸易壁垒（TBT）委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认标准化原则制定的。 ====意义和用途====== 5.1 可对扁平夹层结构进行弯曲试验，以确定夹层弯曲刚度、芯剪切强度和剪切模量，或面板的抗压强度和抗拉强度。评估堆芯抗剪强度的测试也可用于评估堆芯与面板之间的粘结。 5.2 该试验方法仅限于获得夹层板面板的强度和刚度，以及获得用于使用实践计算夹层梁弯曲和剪切刚度的荷载-挠度数据 D7250/D7250M . 由于加载时弯曲试样的曲率，本试验得出的面板抗压强度可能不等于承受纯边缘（平面内）压缩的夹层结构的面板抗压强度。 5.3 岩芯剪切强度和剪切模量最好根据试验方法确定 C273/C273M 提供裸芯材料。试验方法 C393/C393M 也可用于确定堆芯抗剪强度。实践 D7250/D7250M 可用于计算夹层梁的弯曲和剪切刚度。 5.4 该测试方法可用于生成结构设计允许值、材料规范和研发应用的面板强度数据；它也可以用作粘合夹芯板的质量控制测试。 5.5 因此，应报告影响面板强度的因素包括:面板材料、芯材料、粘合材料、材料制造方法、面板堆叠顺序和总厚度、芯几何形状（单元尺寸）、芯密度、粘合厚度、试样几何形状、试样制备、试样调节、测试环境、，试样对齐、加载程序、测试速度、面板孔隙含量、粘合剂孔隙含量和面板体积钢筋百分比。 此外，相同材料的预固化/粘结和共固化面板之间的面板强度可能不同。 注2: 对薄面板和低密度芯的梁施加集中力可能会产生难以解释的结果，尤其是在接近破坏点时。较宽的加载块和橡胶压力垫可能有助于分散力。 注3: 为了确保简单夹层梁理论有效，四点弯曲试验的一个好的经验法则是支撑跨度长度除以夹层厚度应大于20( 序列号 >20）面板厚度与芯层厚度之比小于0.1( 电汇 < 0.1).

1.1 This test method covers determination of facesheet properties of flat sandwich constructions subjected to flexure in such a manner that the applied moments produce curvature of the sandwich facesheet planes and result in compressive and tensile forces in the facesheets. 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 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. 1.2.1 Within the text, the inch-pound units are shown in brackets. 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. Note 1: Alternate procedures for determining the compressive strength of unidirectional polymer matrix composites materials in a sandwich beam configuration may be found in Test Method D5467/D5467M . 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. ====== Significance And Use ====== 5.1 Flexure tests on flat sandwich construction may be conducted to determine the sandwich flexural stiffness, the core shear strength, and shear modulus, or the facesheets’ compressive and tensile strengths. Tests to evaluate core shear strength may also be used to evaluate core-to-facesheet bonds. 5.2 This test method is limited to obtaining the strength and stiffness of the sandwich panel facesheets, and to obtaining load-deflection data for use in calculating sandwich beam flexural and shear stiffness using Practice D7250/D7250M . Due to the curvature of the flexural test specimen when loaded, facesheet compression strength from this test may not be equivalent to the facesheet compression strength of sandwich structures subjected to pure edgewise (in-plane) compression. 5.3 Core shear strength and shear modulus are best determined in accordance with Test Method C273/C273M provided bare core material is available. Test Method C393/C393M may also be used to determine core shear strength. Practice D7250/D7250M may be used to calculate the flexural and shear stiffness of sandwich beams. 5.4 This test method can be used to produce facesheet strength data for structural design allowables, material specifications, and research and development applications; it may also be used as a quality control test for bonded sandwich panels. 5.5 Factors that influence the facesheet strength and shall therefore be reported include the following: facesheet material, core material, adhesive material, methods of material fabrication, facesheet stacking sequence and overall thickness, core geometry (cell size), core density, adhesive thickness, specimen geometry, specimen preparation, specimen conditioning, environment of testing, specimen alignment, loading procedure, speed of testing, facesheet void content, adhesive void content, and facesheet volume percent reinforcement. Further, facesheet strength may be different between precured/bonded and co-cured facesheets of the same material. Note 2: Concentrated forces on beams with thin facesheets and low density cores can produce results that are difficult to interpret, especially close to the failure point. Wider loading blocks and rubber pressure pads may assist in distributing the forces. Note 3: To ensure that simple sandwich beam theory is valid, a good rule of thumb for the four-point bending test is the support span length divided by the sandwich thickness should be greater than 20 ( S/d > 20) with the ratio of facesheet thickness to core thickness less than 0.1 ( t/c < 0.1).