1.1 本试验方法包括测定模式II层间断裂韧性， G IIc公司 ，使用端部缺口弯曲（ENF）测试在模式II剪切载荷下单向纤维增强聚合物基复合材料层压板的( 图1 ). 图1 ENF测试夹具和样本命名法 1.2 该方法仅适用于由单向碳纤维和玻璃纤维增强层压板组成的复合材料。这一有限的范围反映了在循环测试中获得的经验。该试验方法可能对其他类型和类别的复合材料有用； 然而，已注意到某些干扰（参见第节 6. ). 1.3 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。 1.3.1 在文本中，英寸-磅单位显示在括号中。 1.4 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。 1.5 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。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。此外，与试样几何形状或力引入方法无关的模式II层间断裂韧性测量有助于建立复合材料结构损伤容限分析中使用的设计许用值。对非预裂和预裂韧性的了解允许将适当的值用于感兴趣的应用。 5.2 本试验方法可用于以下目的: 5.2.1 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 G IIc公司 一种特殊的复合材料； 5.2.2 定量比较 G IIc公司 对于具有不同成分的复合材料； 5.2.3 定量比较 G IIc公司 从不同批次的特定复合材料中获得，例如，用作材料筛选标准或制定允许的设计； 和 5.2.4 为复合材料损伤容限和耐久性分析制定分层失效标准。

1.1 This test method covers the determination of the mode II interlaminar fracture toughness, G IIc , of unidirectional fiber-reinforced polymer matrix composite laminates under mode II shear loading using the end-notched flexure (ENF) test ( Fig. 1 ). FIG. 1 ENF Test Fixture and Specimen Nomenclature 1.2 This method is limited to use with composites consisting of unidirectional carbon-fiber- and glass-fiber-reinforced laminates. This limited scope reflects the experience gained in round robin testing. This test method may prove useful for other types and classes of composite materials; however, certain interferences have been noted (see Section 6 ). 1.3 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. 1.3.1 Within the text the inch-pound units are shown in brackets. 1.4 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. 1.5 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. Knowledge of a laminated composite material’s resistance to interlaminar fracture is useful for product development and material selection. Furthermore, a measurement of the mode II interlaminar fracture toughness that is independent of specimen geometry or method of force introduction is useful for establishing design allowables used in damage tolerance analyses of composite structures. Knowledge of both the non-precracked and precracked toughnesses allows the appropriate value to be used for the application of interest. 5.2 This test method can serve the following purposes: 5.2.1 To establish quantitatively the effect of fiber surface treatment, local variations in fiber volume fraction, and processing and environmental variables on G IIc of a particular composite material; 5.2.2 To compare quantitatively the relative values of G IIc for composite materials with different constituents; 5.2.3 To compare quantitatively the values of G IIc obtained from different batches of a specific composite material, for example, to use as a material screening criterion or to develop a design allowable; and 5.2.4 To develop delamination failure criteria for composite damage tolerance and durability analyses.