1.1 本试验方法涵盖了直接形成或从片材、板材或成型材料上切割而成的矩形棒形式的连续纤维增强陶瓷复合材料的弯曲性能的测定。三种测试几何形状描述如下: 1.1.1 试验几何结构I- 一种三点加载系统，利用在简支梁上施加的中心点力。 1.1.2 试验几何IIA- 四点加载系统，利用两个与相邻支撑点等距的施力点，施力点之间的距离为支撑跨度的一半。 1.1.3 测试几何IIB- 一种四点加载系统，利用与相邻支撑点等距的两个施力点，施力点之间的距离为- 支撑跨度的三分之一。 1.2 该测试方法主要适用于所有具有连续纤维增强的先进陶瓷基复合材料:单向（1D）、双向（2D）、三向（3D）和其他连续纤维结构。此外，该试验方法也可用于具有连续纤维增强的玻璃（非晶）基复合材料。然而，不能确定那些不会因外部纤维中的张力或压缩而断裂或失效的材料的弯曲强度。该试验方法不直接涉及不连续的纤维增强、晶须增强或颗粒增强陶瓷。使用测试方法可以更好地测试这些类型的陶瓷基复合材料的弯曲性能 C1161年 和 C1211年 。 1.3 测试可以在环境温度或高温下进行。在升高的温度下，需要一个合适的熔炉将试样加热并保持在所需的测试温度下。 1.4 该测试方法包括以下内容: 部分 范围 1. 参考文件 2. 术语 3. 试验方法总结 4 意义和用途 5. 干扰 6 仪器 7. 预防声明 8. 试样 9 程序 10 结果的计算 11 汇报 12 精度和偏差 13 关键词 14 参考文献 CFCC表面状况和精加工 附件A1 将试样热加载到熔炉中的条件和问题 附件A2 应力-应变曲线上的束角补偿 附件A3 弯曲方程中热膨胀的修正 附件A4 测试报告示例 附录X1 1.5 以国际单位制表示的数值应视为符合 IEEE/ASTM SI 10标准 。 1.6 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。 1.7 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 该试验方法用于材料开发、质量控制和材料弯曲规范。尽管弯曲试验方法通常用于确定单片高级陶瓷的设计强度，但强烈反对使用弯曲试验数据来确定CFCC材料的拉伸或压缩性能。弯曲试样中的不均匀应力分布、CFCC在拉伸和压缩方面的不同力学行为、CFCC的低剪切强度以及纤维结构中的各向异性，都导致在将弯曲结果用于CFCC材料设计数据时存在歧义 ( 1个- 4. ) 。 3. 相反，建议在均匀应力试验条件下进行单轴强制拉伸和压缩试验，以开发CFCC材料设计数据。 5.2 在这种测试方法中，弯曲应力是根据弹性梁理论计算的，并简化了材料是均匀的和线性弹性的假设。这适用于主纤维方向与梁轴线重合/横向的复合材料。这些假设对于计算抗弯强度值是必要的，但限制了比较型试验的应用，例如用于材料开发、质量控制和抗弯规范。这种比较试验需要一致和标准化的试验条件，即试样几何形状/厚度、应变速率和大气/试验条件。 5.3 与单片高级陶瓷不同，CFCC通常会因单个主要缺陷而发生灾难性断裂，而累积损伤过程会导致“优雅”断裂。 因此，承受均匀弯曲应力的材料体积可能不是决定CFCC弯曲强度的重要因素。然而，测试统计上显著数量的弯曲试样的需要并没有被消除。由于CFCC中脆性基体和陶瓷纤维强度的概率性质，在每种测试条件下都需要足够数量的试样进行统计分析，并在 9.7 .目前还没有研究确定试样体积对CFCC强度分布的确切影响。 5.4 四点加载几何形状（几何形状IIA和IIB）比三点加载几何形状更可取- 点加载几何图形（几何图形I）。在四点加载几何形状中，与三点加载几何形状相比，试样的大部分受到最大拉伸和压缩应力。如果在测试的特定复合材料系统中存在统计/威布尔特性失效，则最大应力区域的大小将在决定机械性能方面发挥作用。然后，四点几何可以产生更可靠的统计数据。 5.5 弯曲试验提供了材料在复杂弯曲应力条件下的强度和变形信息。在CFCC中，非线性应力-应变行为可能是累积损伤过程的结果（例如，基体开裂、基体/纤维脱胶、纤维断裂、分层等）。 )其可能受到测试模式、测试速率、处理效果或环境影响的影响。其中一些影响可能是应力腐蚀或亚临界（缓慢）裂纹扩展的后果，可以通过以足够快的速率进行测试来将其降至最低，如 10.3 本试验方法的。 5.6 由于几何效应，由特定材料或部件的选定部分或两者按照标准测试尺寸制造的试样的弯曲测试结果不能明确用于定义整个全尺寸最终产品的强度和变形特性或其在不同环境中的使用性能。在将试验结果外推到其他配置和性能条件时，应仔细考虑尺寸和几何形状的影响。 5.7 出于质量控制的目的，标准化弯曲试样的结果可以被视为表明在给定的初级加工条件和后处理热处理下，从中提取试样的材料批次的响应。 5.8 CFCC的弯曲行为和强度取决于其固有的断裂阻力、断裂源的存在、损伤累积过程或其组合。尽管超出了本试验方法的范围，但强烈建议对断裂表面和断口进行分析。

1.1 This test method covers the determination of flexural properties of continuous fiber-reinforced ceramic composites in the form of rectangular bars formed directly or cut from sheets, plates, or molded shapes. Three test geometries are described as follows: 1.1.1 Test Geometry I— A three-point loading system utilizing center point force application on a simply supported beam. 1.1.2 Test Geometry IIA— A four-point loading system utilizing two force application points equally spaced from their adjacent support points, with a distance between force application points of one-half of the support span. 1.1.3 Test Geometry IIB— A four-point loading system utilizing two force application points equally spaced from their adjacent support points, with a distance between force application points of one-third of the support span. 1.2 This test method applies primarily to all advanced ceramic matrix composites with continuous fiber reinforcement: unidirectional (1D), bidirectional (2D), tridirectional (3D), and other continuous fiber architectures. In addition, this test method may also be used with glass (amorphous) matrix composites with continuous fiber reinforcement. However, flexural strength cannot be determined for those materials that do not break or fail by tension or compression in the outer fibers. This test method does not directly address discontinuous fiber-reinforced, whisker-reinforced, or particulate-reinforced ceramics. Those types of ceramic matrix composites are better tested in flexure using Test Methods C1161 and C1211 . 1.3 Tests can be performed at ambient temperatures or at elevated temperatures. At elevated temperatures, a suitable furnace is necessary for heating and holding the test specimens at the desired testing temperatures. 1.4 This test method includes the following: Section Scope 1 Referenced Documents 2 Terminology 3 Summary of Test Method 4 Significance and Use 5 Interferences 6 Apparatus 7 Precautionary Statement 8 Test Specimens 9 Procedures 10 Calculation of Results 11 Report 12 Precision and Bias 13 Keywords 14 References CFCC Surface Condition and Finishing Annex A1 Conditions and Issues in Hot Loading of Test Specimens into Furnaces Annex A2 Toe Compensation on Stress-Strain Curves Annex A3 Corrections for Thermal Expansion in Flexural Equations Annex A4 Example of Test Report Appendix X1 1.5 The values stated in SI units are to be regarded as the standard in accordance with IEEE/ASTM SI 10 . 1.6 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. 1.7 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 This test method is used for material development, quality control, and material flexural specifications. Although flexural test methods are commonly used to determine design strengths of monolithic advanced ceramics, the use of flexure test data for determining tensile or compressive properties of CFCC materials is strongly discouraged. The nonuniform stress distributions in the flexure test specimen, the dissimilar mechanical behavior in tension and compression for CFCCs, low shear strengths of CFCCs, and anisotropy in fiber architecture all lead to ambiguity in using flexure results for CFCC material design data ( 1- 4 ) . 3 Rather, uniaxial-forced tensile and compressive tests are recommended for developing CFCC material design data based on a uniformly stressed test condition. 5.2 In this test method, the flexure stress is computed from elastic beam theory with the simplifying assumptions that the material is homogeneous and linearly elastic. This is valid for composites where the principal fiber direction is coincident/transverse with the axis of the beam. These assumptions are necessary to calculate a flexural strength value, but limit the application to comparative type testing such as used for material development, quality control, and flexure specifications. Such comparative testing requires consistent and standardized test conditions, that is, test specimen geometry/thickness, strain rates, and atmospheric/test conditions. 5.3 Unlike monolithic advanced ceramics which fracture catastrophically from a single dominant flaw, CFCCs generally experience “graceful” fracture from a cumulative damage process. Therefore, the volume of material subjected to a uniform flexural stress may not be as significant a factor in determining the flexural strength of CFCCs. However, the need to test a statistically significant number of flexure test specimens is not eliminated. Because of the probabilistic nature of the strength of the brittle matrices and of the ceramic fiber in CFCCs, a sufficient number of test specimens at each testing condition is required for statistical analysis, with guidelines for sufficient numbers provided in 9.7 . Studies to determine the exact influence of test specimen volume on strength distributions for CFCCs are not currently available. 5.4 The four-point loading geometries (Geometries IIA and IIB) are preferred over the three-point loading geometry (Geometry I). In the four-point loading geometry, a larger portion of the test specimen is subjected to the maximum tensile and compressive stresses, as compared to the three-point loading geometry. If there is a statistical/Weibull character failure in the particular composite system being tested, the size of the maximum stress region will play a role in determining the mechanical properties. The four-point geometry may then produce more reliable statistical data. 5.5 Flexure tests provide information on the strength and deformation of materials under complex flexural stress conditions. In CFCCs nonlinear stress-strain behavior may develop as the result of cumulative damage processes (for example, matrix cracking, matrix/fiber debonding, fiber fracture, delamination, etc.) which may be influenced by testing mode, testing rate, processing effects, or environmental influences. Some of these effects may be consequences of stress corrosion or subcritical (slow) crack growth which can be minimized by testing at sufficiently rapid rates as outlined in 10.3 of this test method. 5.6 Because of geometry effects, the results of flexure tests of test specimens fabricated to standardized test dimensions from a particular material or selected portions of a component, or both, cannot be categorically used to define the strength and deformation properties of the entire, full-size end product or its in-service behavior in different environments. The effects of size and geometry shall be carefully considered in extrapolating the test results to other configurations and performance conditions. 5.7 For quality control purposes, results from standardized flexure test specimens may be considered indicative of the response of the material lot from which they were taken with the given primary processing conditions and post-processing heat treatments. 5.8 The flexure behavior and strength of a CFCC are dependent on its inherent resistance to fracture, the presence of fracture sources, damage accumulation processes, or combinations thereof. Analysis of fracture surfaces and fractography, though beyond the scope of this test method, is highly recommended.