1.1 本试验方法使用90°弯曲梁试样测定连续纤维增强复合材料的弯曲梁强度( 无花果。1和 2. ). 弯曲梁由两个直腿组成，通过90°弯曲连接，弯曲度为6.4 毫米[0.25英寸]内半径。施加力时，试样的弯曲区域会产生平面外（穿过厚度）拉应力。本试验方法仅限于用于由织物层或单向纤维层组成的复合材料。 图1 试样几何形状（国际单位制） 图2 试样几何形状（英寸- 磅） 1.2 如果在纤维沿支腿和弯曲处连续运行的情况下使用单向试样，则本试验方法也可用于测量层间拉伸强度。 1.3 本试验方法仅限于用于由织物层或单向纤维层组成的复合材料。 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 分层敏感性是许多先进复合材料层合结构的主要设计问题之一。复杂的结构几何形状可能会导致平面外应力，这可能很难分析。当加载弯曲的结构细节时，变形导致曲率半径增加，可能会导致层间拉应力和分层。层合复合材料抗层间断裂的知识对于产品开发和材料选择非常有用。涉及out的失效标准和设计允许值- 平面应力的计算可能不容易获得，或验证较差，需要额外的实验数据。 5.2 本试验方法可用于以下目的: 5.2.1 测量弯曲梁强度； 5.2.2 当使用单向试样时，测量层间强度，其中所有纤维相对于试样的长直边定向0°； 5.2.3 定量确定纤维表面处理、纤维体积分数的局部变化以及加工和环境变量对曲梁强度或层间强度的影响（通过- 特定复合材料的厚度）抗拉强度； 5.2.4 定量比较不同成分复合材料的相对曲梁强度或层间拉伸强度； 5.2.5 定量比较从不同批次的特定复合材料中获得的曲梁强度或层间抗拉强度值，例如，用作材料筛选标准、用于质量保证或制定允许的设计； 5.2.6 生成平面外结构失效数据，用于结构设计和分析； 和 5.2.7 制定失效标准，以预测平面外应力引起的失效。

1.1 This test method determines the curved beam strength of a continuous fiber-reinforced composite material using a 90° curved beam specimen ( Figs. 1 and 2 ). The curved beam consists of two straight legs connected by a 90° bend with a 6.4 mm [0.25 in.] inner radius. An out-of-plane (through-the-thickness) tensile stress is produced in the curved region of the specimen when force is applied. This test method is limited to use with composites consisting of layers of fabric or layers of unidirectional fibers. FIG. 1 Test Specimen Geometry (SI units) FIG. 2 Test Specimen Geometry (inch-pound) 1.2 This test method may also be used to measure the interlaminar tensile strength if a unidirectional specimen is used where the fibers run continuously along the legs and around the bend. 1.3 This test method is limited to use with composites consisting of layers of fabric or layers of unidirectional fibers. 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 Susceptibility to delamination is one of the major design concerns for many advanced laminated composite structures. Complex structural geometries can result in out-of-plane stresses, which may be difficult to analyze. When curved structural details are loaded such that the deformation results in an increase in the radius of curvature, interlaminar tensile stress and delaminations can result. Knowledge of a laminated composite material’s resistance to interlaminar fracture is useful for product development and material selection. Failure criteria and design allowables involving out-of-plane stresses may not be readily available or may be poorly validated, requiring additional experimental data. 5.2 This test method can serve the following purposes: 5.2.1 To measure a curved-beam strength; 5.2.2 To measure an interlaminar strength when using a unidirectional specimen where all fibers are oriented 0° relative to the long straight edges of the specimen; 5.2.3 To establish quantitatively the effect of fiber surface treatment, local variations in fiber volume fraction, and processing and environmental variables on the curved beam strength or the interlaminar (through-the-thickness) tensile strength of a particular composite material; 5.2.4 To compare quantitatively the relative curved-beam strength or interlaminar tensile strengths of composite materials with different constituents; 5.2.5 To compare quantitatively the values of the curved-beam strength or interlaminar tensile strengths obtained from different batches of a specific composite material, for example, to use as a material screening criterion, to use for quality assurance, or to develop a design allowable; 5.2.6 To produce out-of-plane structural failure data for structural design and analysis; and 5.2.7 To develop failure criteria for predicting failures caused by out-of-plane stresses.