1.1 本试验方法确定了循环次数( N )对于基于开放模式I循环应变能释放率的分层增长开始( G )，使用双悬臂梁（DCB）试样，如所示 图1 . 本试验方法适用于连续纤维增强复合材料的恒幅拉伸疲劳载荷。当本试验方法应用于不同温度下的多个试样时 G -水平，结果可显示为 G–N 曲线，如所示 图2 . 图1 带钢琴铰链的DCB试样 图。 2. G–N 曲线 1.2 本试验方法仅适用于由单向碳纤维带层压板和单相聚合物基体组成的复合材料。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，但已注意到某些干扰（见试验方法第6.5节） D5528 ). 1.3 以国际单位制表示的数值应视为标准值。本标准不包括其他计量单位。 1.3.1 例外情况- 括号中提供的值仅供参考。 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层合复合材料结构的主要缺点之一。了解层压复合材料在疲劳载荷下抵抗层间断裂的能力有助于产品开发和材料选择。此外，测量模式I循环应变能释放率和循环次数与分层增长开始的关系， G–N 与试样几何形状或荷载引入方法无关，这有助于建立由这些材料制成的复合材料结构损伤容限分析中使用的设计许用值。 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–N 一种特殊的复合材料。 5.2.2 定量比较 G–N 用于具有不同成分的复合材料。 5.2.3 为复合材料损伤容限和耐久性分析制定避免疲劳载荷下分层增长的标准。

1.1 This test method determines the number of cycles ( N ) for the onset of delamination growth based on the opening mode I cyclic strain energy release rate ( G ), using the Double Cantilever Beam (DCB) specimen shown in Fig. 1 . This test method applies to constant amplitude, tension-tension fatigue loading of continuous fiber-reinforced composite materials. When this test method is applied to multiple specimens at various G -levels, the results may be shown as a G–N curve, as illustrated in Fig. 2 . FIG. 1 DCB Specimen with Piano Hinges FIG. 2 G–N Curve 1.2 This test method is limited to use with composites consisting of unidirectional carbon fiber tape laminates with single-phase polymer matrices. 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 6.5 of Test Method D5528 ). 1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.3.1 Exception— The values provided in parentheses are for information only. 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 weaknesses of many advanced laminated composite structures. Knowledge of a laminated composite material's resistance to interlaminar fracture under fatigue loads is useful for product development and material selection. Furthermore, a measurement of the relationship of the mode I cyclic strain energy release rate and the number of cycles to delamination growth onset, G–N , that is independent of specimen geometry or method of load introduction, is useful for establishing design allowables used in damage tolerance analyses of composite structures made from these materials. 5.2 This test method can serve the following purposes: 5.2.1 To establish quantitatively the effects of fiber surface treatment, local variations in fiber volume fraction, and processing and environmental variables on G–N of a particular composite material. 5.2.2 To compare quantitatively the relative values of G–N for composite materials with different constituents. 5.2.3 To develop criteria for avoiding the onset of delamination growth under fatigue loading for composite damage tolerance and durability analyses.