1.1 本规程涵盖了测定聚合物基复合材料锥形或阶梯状粘结接头抗压强度的程序。它适用于具有单向层或机织物增强材料的二次粘合或共粘合层压板。要粘合的材料可能是不同的系统。在粘合线中，可以使用也可以不使用单独的粘合材料（例如:粘合剂可以与预浸料系统一起使用，也可以不与湿铺层修补系统一起使用）。可接受的测试层压板和厚度范围如所述 8.2.7 . 标准修复类型与实际拉伸载荷相同 D8131/D8131M . 虽然本规程未明确涵盖外部补丁修复，但这些修复可以作为非- 使用本规程的标准试样。 1.2 本规程补充了试验方法 D7249/D7249M 用于通过长梁弯曲对面板夹层结构施加压缩载荷。几个重要的试样参数（例如，接头长度、铺层重叠、台阶深度和锥度比）不受本规程的约束；然而，需要指定和报告这些参数，以支持可重复的结果。 1.3 可以测试单向（0°铺层方向）复合材料以及多向复合材料层压板和织物复合材料。 1.4 单位- 以国际单位制或英寸-磅单位表示的数值应单独视为标准值。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。 1.4.1 在文本中，英寸-磅单位显示在括号中。 1.5 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。 1.6 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 可以对平面夹芯板结构进行弯曲试验，以确定面板嵌缝或阶梯接缝抗压强度。 5.2 该实践仅限于获得夹层板嵌条和阶梯接缝面板的抗压强度。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 因此，应报告影响压缩响应的因素包括:材料（层压板、芯材和粘合剂）；材料制造方法；材料制备方法，包括粘接前的表面处理，铺设- up、试样面板堆叠顺序和总厚度；核心几何形状（单元大小）；芯密度；粘合剂厚度；接头锥度比或步长；铺层重叠长度；母层和修复层压板的相对厚度和刚度；粘接刚度；试样制备；样本调节；测试环境；样本对齐；测试速度；温度下的时间；孔隙含量；和体积百分比增强。可从本规程中获得的试验方向上的特性包括: 5.3.1 极限抗压强度（基于标称修复材料厚度）( F r 铜 ). 5.3.2 每层极限运行荷载( N j ). 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）修补材料面板厚度与芯层厚度之比小于0.1( h r /c < 0.1).

1.1 This practice covers the procedure for determination of the compressive strength of a tapered or stepped bonded joint of polymer matrix composite materials. It is applicable to secondary bonded or co-bonded laminates with either unidirectional plies or woven fabric reinforcements. The materials to be bonded may be different systems. In the bondline, a separate adhesive material may or may not be used (example: adhesives may be used with a prepreg system or may not be used with a wet lay-up repair system). The range of acceptable test laminates and thicknesses are described in 8.2.7 . The standard repair types are the same as for the tensile loading in Practice D8131/D8131M . While external patch repairs are not explicitly covered in this practice, these repairs could be tested as a non-standard specimen using this practice. 1.2 This practice supplements Test Method D7249/D7249M for compressive loading of facesheet sandwich constructions by long beam flexure. Several important test specimen parameters (for example, joint length, ply overlaps, step depth, and taper ratio) are not mandated by this practice; however, these parameters are required to be specified and reported to support repeatable results. 1.3 Unidirectional (0° ply orientation) composites as well as multi-directional composite laminates and fabric composites, can be tested. 1.4 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. 1.4.1 Within the text, the inch-pound units are shown in brackets. 1.5 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. 1.6 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 panel construction may be conducted to determine facesheet scarf or step joint compressive strength. 5.2 This practice is limited to obtaining the compressive strength of the sandwich panel scarf and step joint facesheets. 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 Factors that influence the compressive response and should therefore be reported include the following: materials (laminate facesheet, core, and adhesive); methods of material fabrication; methods of material preparation, including surface preparation prior to bonding, lay-up, specimen facesheet stacking sequence, and overall thickness; core geometry (cell size); core density; adhesive thickness; joint taper ratio or step length; ply overlap length; relative thickness and stiffness of parent and repair laminates; adhesive bond stiffness; specimen preparation; specimen conditioning; environment of testing; specimen alignment; speed of testing; time at temperature; void content; and volume percent reinforcement. Properties, in the test direction, which may be obtained from this practice, include the following: 5.3.1 Ultimate compressive strength (based on the nominal repair material thickness), ( F r cu ). 5.3.2 Ultimate running load per ply, ( N j ). 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 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 repair material facesheet thickness to core thickness less than 0.1 ( h r /c < 0.1).