1.1 本试验方法包括层间断裂韧性的测定， G c ，使用混合模式弯曲（MMB）测试，在不同模式I至模式II加载比下连续纤维增强复合材料的。 1.2 本试验方法仅适用于由具有脆性和韧性单相聚合物基体的单向碳纤维带层压板组成的复合材料。该试验方法还限于测定从分层插入物开始的断裂韧性。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的韧性值和其他类别的复合材料有用； 然而，已注意到某些干扰（参见第节 6. ). 该测试方法已成功用于测试玻璃纤维复合材料和粘接接头的韧性。 1.3 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 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。复合材料层间断裂抗力的知识有助于产品开发和材料选择。由于分层可以通过各种模式混合的载荷来承受和扩展，因此在各种模式混合下测量复合材料的韧性很重要。 韧性轮廓，其中断裂韧性绘制为模式混合的函数（参见 图3 )，有助于建立用于这些材料制成的复合材料结构损伤容限分析的失效准则。 图3 混合模式摘要图 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 c 在各种模式混合下的特定复合材料， 5.2.2 定量比较 G c 不同成分复合材料的模式混合，以及 5.2.3 为复合材料损伤容限和耐久性分析制定分层失效标准。 5.3 该方法可用于确定以下分层韧性值: 5.3.1 分层起始- 应报告两个分层起始值:( 1. )在荷载-位移曲线（NL）和( 2. )合规性增加了5 % 或者荷载已达到最大值（5%/最大值），这取决于沿荷载-挠度曲线最先出现的值（参见 图4 ). 分层起始的每个定义都与其自身的 G c 和 G 二、 / G 根据相应临界点的负荷计算。 5%/最大值 G c 值通常是三个值中最具再现性的 G c 价值观然而，NL值是更保守的数字。当选择收集传播值时（请参阅 5.3.2 )，可以在第一次目测到分层在试样边缘生长的点处报告第三个起始值。VIS点通常介于NL和5%/最大点之间。 图4 荷载-位移曲线 5.3.2 传播选项- 在MMB测试中，分层将从插件以稳定或不稳定的方式增长，具体取决于测试的模式混合。作为一种选择，当分层以稳定的方式增长时，可以收集传播韧性值。 当分层以不稳定的方式增长时，无法获得传播韧性值。传播韧性值可能会受到光纤桥接的严重影响，这是零度类型试样的伪影 ( 3- 5. ) . 由于它们通常被认为是人为的，因此在报告时必须清楚地标记传播值。传播值的一种用途是检查分层插入的问题。通常，随着分层扩展和纤维桥接的发展，分层韧性值从起始值开始升高。当韧性值随着分层的增加而降低时，分层插入不良通常是原因。 分层可能太厚或变形，导致插入件末端形成树脂袋。为了获得准确的起始值，正确植入并检查分层插件至关重要（参见 8.2 ). 5.3.3 预裂韧性- 在极少数情况下，随着分层的传播，韧性可能会从起始值下降（参见 5.3.2 ). 如果出现这种情况，应检查分层，以确保其符合中的插入建议 8.2 . 只有在验证韧性下降不是由于插入不良所致后，才应将预裂纹视为一种选择。在预裂纹情况下，分层首先在模式I、模式II或混合模式下从插件扩展。 然后在所需的模式混合下重新加载试样，以获得韧性值。

1.1 This test method covers the determination of interlaminar fracture toughness, G c , of continuous fiber-reinforced composite materials at various Mode I to Mode II loading ratios using the Mixed-Mode Bending (MMB) Test. 1.2 This test method is limited to use with composites consisting of unidirectional carbon fiber tape laminates with brittle and tough single-phase polymer matrices. This test method is further limited to the determination of fracture toughness as it initiates from a delamination insert. This limited scope reflects the experience gained in round robin testing. This test method may prove useful for other types of toughness values and for other classes of composite materials; however, certain interferences have been noted (see Section 6 ). This test method has been successfully used to test the toughness of both glass fiber composites and adhesive joints. 1.3 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 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 the interlaminar fracture resistance of composites is useful for product development and material selection. Since delaminations can be subjected to and extended by loadings with a wide range of mode mixtures, it is important that the composite toughness be measured at various mode mixtures. The toughness contour, in which fracture toughness is plotted as a function of mode mixtures (see Fig. 3 ), is useful for establishing failure criterion used in damage tolerance analyses of composite structures made from these materials. FIG. 3 Mixed-Mode Summary Graph 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 c of a particular composite material at various mode mixtures, 5.2.2 To compare quantitatively the relative values of G c versus mode mixture for composite materials with different constituents, and 5.2.3 To develop delamination failure criteria for composite damage tolerance and durability analyses. 5.3 This method can be used to determine the following delamination toughness values: 5.3.1 Delamination Initiation— Two values of delamination initiation shall be reported: ( 1 ) at the point of deviation from linearity in the load-displacement curve (NL) and ( 2 ) at the point at which the compliance has increased by 5 % or the load has reached a maximum value (5%/max) depending on which occurs first along the load deflection curve (see Fig. 4 ). Each definition of delamination initiation is associated with its own value of G c and G II / G calculated from the load at the corresponding critical point. The 5%/Max G c value is typically the most reproducible of the three G c values. The NL value is, however, the more conservative number. When the option of collecting propagation values is taken (see 5.3.2 ), a third initiation value may be reported at the point at which the delamination is first visually observed to grow on the edge of the specimen. The VIS point often falls between the NL and the 5%/Max points. FIG. 4 Load-Displacement Curves 5.3.2 Propagation Option— In the MMB test, the delamination will grow from the insert in either a stable or an unstable manner depending on the mode mixture being tested. As an option, propagation toughness values may be collected when delaminations grow in a stable manner. Propagation toughness values are not attainable when the delamination grows in an unstable manner. Propagation toughness values may be heavily influenced by fiber bridging which is an artifact of the zero-degree-type test specimen ( 3- 5 ) . Since they are often believed to be artificial, propagation values must be clearly marked as such when they are reported. One use of propagation values is to check for problems with the delamination insert. Normally, delamination toughness values rise from the initiation values as the delamination propagates and fiber bridging develops. When toughness values decrease as the delamination grows, a poor delamination insert is often the cause. The delamination may be too thick or deformed in such a way that a resin pocket forms at the end of the insert. For accurate initiation values, a properly implanted and inspected delamination insert is critical (see 8.2 ). 5.3.3 Precracked Toughness— Under rare circumstances, toughness may decrease from the initiation values as the delamination propagates (see 5.3.2 ). If this occurs, the delamination should be checked to ensure that it complies with the insert recommendations found in 8.2 . Only after verifying that the decreasing toughness was not due to a poor insert, should precracking be considered as an option. With precracking, a delamination is first extended from the insert in Mode I, Mode II, or mixed mode. The specimen is then reloaded at the desired mode mixture to obtain a toughness value.