ASTM C1940
1.1 本试验方法描述了测定连续纤维增强陶瓷基复合材料（CMC）临界模式I层间应变能释放率的实验方法和程序，具体如下 G Ic 该特性有时也被描述为I型断裂韧性或I型断裂阻力。 1.2 该试验方法主要适用于具有二维层压板结构的陶瓷基复合材料，该结构由在脆性陶瓷基体内的单向带或二维编织织物结构中的连续陶瓷纤维的叠层组成。 1.3 该试验方法确定了在两个薄层或层之间的层间界面处分层生长时产生的每单位新表面积释放的弹性应变能。在本试验方法中，术语分层专门指代这种类型的生长，而术语裂纹是一个更通用的术语，也可以指代基体开裂、层内分层生长或纤维断裂。 1.4 该试验方法使用双悬臂梁（DCB）试样来确定临界模式I层间应变能量释放率( G Ic ).根据测试方法，聚合物基复合材料（PMCs）的DCB测试方法已标准化 D5528 该试验方法采用了类似的程序，但进行了修改，以说明CMC与PMCs相比的不同物理性能、钢筋结构、应力-应变响应和失效机制。 1.5 本测试适用于环境温度和大气测试条件，但该测试方法也可用于高温或环境暴露测试，使用适当的环境测试箱、用于控制和测量测试箱温度、湿度和大气的测量设备、高温夹具、，以及用于测量分层生长的改良设备。 1.6 以国际单位制表示的数值应视为标准。本标准不包括其他计量单位。 1.6.1 本试验方法中表达的数值符合国际单位制（SI）和 IEEE/ASTM SI 10 . 1.7 本标准并不旨在解决与其使用相关的所有安全问题（如有）。本标准的使用者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。 具体危害说明见第节 8. . 1.8 本国际标准是根据世界贸易组织技术性贸易壁垒委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认的标准化原则制定的。 ====意义和用途====== 5.1 层间分层生长可能是层合CMC结构中的一种关键失效模式。了解层合CMC的层间分层生长阻力对于材料开发和选择以及CMC部件设计至关重要。 （请参阅 ( 1- 8. ) 3. 哪些给出 G Ic 值为20 J/m 2. 至800 J/m 2. 适用于环境温度下的不同CMC和碳-碳复合材料系统。） 5.2 进行此测试会产生多个值 G Ic 其传统上相对于测量该值时的分层长度绘制（参见 图2 ).对测试请求者有价值的特定数据将取决于激发测试的最终用途。 5.2.1 从预植入插入物或机加工切口开始的第一次生长增量有时被描述为非预裂纹（NPC）韧性。NPC韧性可能令人感兴趣，因为它可以代表制造或加工缺陷，如层压板中的异物碎屑或加工过程中的错误。 5.2.2 假设在第一次增量之后出现的尖锐裂纹尖端开始的下一次增长增量有时被定义为预裂纹（PC）韧性。PC韧性可能令人感兴趣，因为它更能代表对自然发生或损伤引起的分层生长的抵抗力。 5.2.3 剩余的增长增量共同形成R曲线，提供了如何 G Ic 随着分层的进展而演变。在单向带层压板中，由于嵌套纤维在分层平面上的桥接，R曲线通常会增加，人为地增加 G Ic 对于几乎没有层间嵌套的2-D编织层压板，R曲线可以是平坦的。 5.2.4 R曲线平坦的增长增量，以及 G Ic 已达到稳定状态值，定义为 G IR ，可能是感兴趣的，并且也可能在设计和分析中有用。 5.3 此测试方法用于测量 G Ic CMC材料的用途如下: 5.3.1 定量确定CMC材料变量（纤维界面涂层、基体结构和孔隙率、纤维结构、加工和环境变量、调理/暴露处理等）的影响。 )在 G Ic 以及特定CMC材料的层间裂纹扩展和损伤机制； 5.3.2 要确定CMC材料是否显示R曲线行为，其中 G Ic 随着裂纹扩展而变化，或者在给定的分层生长量下达到稳定值。 图2 显示了SiC-SiC复合材料的R曲线行为 ( 1. ) ; 5.3.3 为CMC损伤容限、耐久性或可靠性分析和寿命预测制定分层失效标准和设计容许值； 注3: 只有在确信测试产生的是材料特性而不是结构几何形状的情况下，才能可靠地将测试数据用于此目的- 依赖，财产。 5.3.4 定量比较的相对值 G Ic 对于具有不同成分和材料性能、增强结构、加工参数或环境暴露条件的不同CMC材料；和 5.3.5 定量比较的值 G Ic 从不同批次的特定CMC材料中获得，以进行批次验收质量控制，用作材料筛选标准，或评估批次变异性。
1.1 This test method describes the experimental methods and procedures for the determination of the critical mode I interlaminar strain energy release rate of continuous fiber- reinforced ceramic matrix composite (CMC) materials in terms of G Ic . This property is also sometimes described as the mode I fracture toughness or the mode I fracture resistance. 1.2 This test method applies primarily to ceramic matrix composite materials with a 2-D laminate structure, consisting of lay-ups of continuous ceramic fibers, in unidirectional tape or 2-D woven fabric architectures, within a brittle ceramic matrix. 1.3 This test method determines the elastic strain energy released per unit of new surface area created as a delamination grows at the interlaminar interface between two lamina or plies. The term delamination is used in this test method to specifically refer to this type of growth, while the term crack is a more general term that can also refer to matrix cracking, intralaminar delamination growth, or fiber fracture. 1.4 This test method uses a double cantilever beam (DCB) specimen to determine the critical mode I interlaminar strain energy release rate ( G Ic ). A DCB test method has been standardized for polymer matrix composites (PMCs) under Test Method D5528 . This test method addresses a similar procedure, but with modifications to account for the different physical properties, reinforcement architectures, stress-strain response, and failure mechanisms of CMCs compared to PMCs. 1.5 This test is written for ambient temperature and atmospheric test conditions, but the test method can also be used for elevated temperature or environmental exposure testing with the use of an appropriate environmental test chamber, measurement equipment for controlling and measuring the chamber temperature, humidity, and atmosphere, high temperature gripping fixtures, and modified equipment for measuring delamination growth. 1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.6.1 Values expressed in this test method are in accordance with the International System of Units (SI) and IEEE/ASTM SI 10 . 1.7 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. Specific hazard statements are given in Section 8 . 1.8 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 Interlaminar delamination growth can be a critical failure mode in laminated CMC structures. Knowledge of the resistance to interlaminar delamination growth of a laminated CMC is essential for material development and selection, and for CMC component design. (See ( 1- 8 ) 3 which give G Ic values of 20 J/m 2 to 800 J/m 2 for different CMC and carbon-carbon composite systems at ambient temperatures.) 5.2 Conducting this test produces multiple values of G Ic which are traditionally plotted against the delamination length at which that value was measured (see Fig. 2 ). The specific data of value to the test requestor will depend on the end use that motivated testing. 5.2.1 The first increment of growth, initiated from a pre-implanted insert or machined notch, is sometimes described as the non-precracked (NPC) toughness. NPC toughness may be of interest, as it can represent manufacturing or processing defects, such as foreign object debris in a laminate or an error during machining. 5.2.2 The next increment of growth, initiated from the sharp crack tip assumed to be present after the first increment, is sometimes defined as the precracked (PC) toughness. PC toughness may be of interest, as it is more representative of the resistance to delamination growth from a naturally occurring or damage-induced delamination. 5.2.3 The remaining increments of growth, collectively forming an R-curve, provide information on how G Ic evolves as the delamination advances. In unidirectional tape laminates, the R-curve is often increasing due to bridging of nested fibers across the delamination plane, artificially increasing G Ic . For 2-D woven laminates for which there is little interply nesting, the R-curve may be flat. 5.2.4 The increments of growth in which the R-curve is flat, and G Ic has reached a steady state value defined as G IR , may be of interest and may also useful in design and analysis. 5.3 This test method for measurement of G Ic of CMC materials can serve the following purposes: 5.3.1 To establish quantitatively the effect of CMC material variables (fiber interface coatings, matrix structure and porosity, fiber architecture, processing and environmental variables, conditioning/exposure treatments, etc.) on G Ic and the interlaminar crack growth and damage mechanisms of a particular CMC material; 5.3.2 To determine if a CMC material shows R-curve behavior where G Ic changes with crack extension or reaches a stable value at a given amount of delamination growth. Fig. 2 shows R-curve behavior for a SiC-SiC composite ( 1 ) ; 5.3.3 To develop delamination failure criteria and design allowables for CMC damage tolerance, durability or reliability analyses, and life prediction; Note 3: Test data can only reliably be used for this purpose if there is confidence that the test is yielding a material property and not a structural, geometry-dependent, property. 5.3.4 To compare quantitatively the relative values of G Ic for different CMC materials with different constituents and material properties, reinforcement architectures, processing parameters, or environmental exposure conditions; and 5.3.5 To compare quantitatively the values of G Ic obtained from different batches of a specific CMC material, to perform lot acceptance quality control, to use as a material screening criterion, or to assess batch variability.
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