1.1 本试验方法涵盖在环境温度下连续纤维增强高级陶瓷管在单调载荷下的弯曲强度测定，包括应力应变响应。本试验方法涉及管状试样几何形状、试样/夹具制造方法、试验模式（力、位移或应变控制）、试验速率（力速率、应力速率、位移速率或应变率）以及数据收集和报告程序。 1.2 在本试验方法中，具有规定量规截面和已知壁厚的先进陶瓷复合管/圆柱体在四点加载系统中受到四点弯曲，同时使用两个力施加点进行支撑，两个力施加点间隔一个内跨距离，该力施加点位于两个支撑点之间的中心，两个支撑点间隔一个外跨距离。施加的横向力在管的标准截面中产生恒定力矩，并产生单轴弯曲应力- 记录复合管的应变响应，直到管发生故障。弯曲强度和弯曲断裂强度分别由产生的最大力和断裂时的力确定。弯曲应变、弯曲比例极限应力和纵向弯曲弹性模量由应力-应变数据确定。注意，本试验方法中使用的弯曲强度是指通过引入单调施加的横向力在管道纵向产生的最大拉伸应力，其中“单调”是指从试验开始到最终断裂没有反转的连续、不间断的试验速率。弯曲强度有时用于估计材料的抗拉强度。 1.3 本试验方法适用于具有连续纤维增强的先进陶瓷基复合管:单向（1D，纤维缠绕和胶带铺设- 向上）、双向（2D、织物/胶带叠层和编织）和三向（3D、编织和编织）。这些类型的陶瓷基复合材料可以由多种晶体和非晶陶瓷基成分（氧化物、碳化物、氮化物、碳、石墨和其他成分）中的多种陶瓷纤维组成。该试验方法也适用于某些类型的功能梯度管，例如由整体高级陶瓷组成的陶瓷纤维缠绕管。本试验方法的目的不是规定或规范材料制造，包括纤维层叠或组成复合材料的层数，而是提供一种适当且一致的方法，用于识别不同制造或纤维层叠方法对产生的管状几何形状弯曲行为的影响。 1.4 本试验方法不直接处理不连续纤维- 增强、晶须增强或颗粒增强陶瓷，但如果可以证明这些材料表现出连续纤维增强陶瓷的损伤容限行为，则此处详述的测试方法可能同样适用于这些复合材料。 1.5 该试验方法适用于基于预期应用的一系列试样管几何形状，包括复合材料特性和管半径。因此，典型测试设置没有“标准”试样几何形状。确定复合管长度、内跨长度和外跨长度，以提供具有均匀弯矩的标距长度。材料特性、管半径、壁厚、管长度以及内外跨段长度的广泛组合是可能的。 1.5.1 本试验方法适用于环境温度试验。高温测试要求高- 具有温度控制和测量系统的温度炉和加热装置，以及本试验方法中未提及的具有温度能力的试验方法。 1.6 本试验方法在以下章节中阐述了管状试样几何形状、试样制备方法、试验速率（即诱导施加力矩速率）以及数据收集和报告程序: 范围 部分 1. 参考文件 部分 2. 术语 部分 3. 试验方法总结 部分 4. 意义和用途 部分 5. 干扰 部分 6. 仪器 部分 7. 危害 部分 8. 试样 部分 9 试验程序 部分 10 计算结果 部分 11 汇报 部分 12 精度和偏差 部分 13 关键词 部分 14 附录 弯曲试验配置概述 附录X1 带支架的固定装置 附录X2 1.7 本试验方法中表示的数值符合国际单位制（SI）和 IEEE/ASTM SI 10 . 1.8 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。 第节给出了具体的危险说明 8. . 1.9 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 该试验方法可用于材料开发、材料比较、质量保证、表征和设计数据生成。 5.2 连续纤维增强陶瓷复合材料（CFCC）可以由连续陶瓷组成- 纤维定向（1D、2D和3D）增强体，通常包含在具有受控孔隙率的细粒度（<50µm）陶瓷基体中。通常，这些复合材料在纤维上有一层工程化的薄（0.1至10µm）界面涂层，以产生裂纹偏转和纤维拔出。 5.3 CFCC组件具有材料特性、界面涂层、孔隙率控制、复合结构（1D、2D和3D）和几何形状的独特和协同组合，这些通常是不可分割的。通过将CFCC平板的测量特性应用于管的设计，可能无法预测CFCC管的机械性能（尤其是编织和3D编织结构）。这是因为制造/加工方法可能是管特有的，无法复制到平板上，从而产生成分相似但结构和形态不同的氟氯化碳材料。特别是，由CFCC材料组成的管状组件形成了材料、几何形状和加固结构的独特协同组合，通常是不可分割的。 换言之，通常无法使用平板测量的特性来预测CFCC管的机械性能。横向加载CFCC管的强度测试提供了受单轴非均匀应力影响的材料的机械行为和强度信息。 5.4 与因单一主要缺陷而发生灾难性断裂的单片高级陶瓷不同，CMC通常在累积损伤过程中经历“优雅”断裂。因此，虽然承受横向加载管试验的不均匀单轴弯曲应力的材料体积可能是确定基体开裂应力的重要因素，但相同体积可能不是确定CMC极限强度的重要因素。然而，复合材料脆性基体强度分布的概率性质要求统计分析和设计的试样数量具有统计学意义。 确定试样体积对复合材料强度分布的确切影响的研究尚未完成。应注意的是，由于这些体积效应，使用不同推荐试样获得的拉伸弯曲强度可能会有所不同。实践 C1683 提供有关强度统计参数缩放的指导，以说明有效体积、有效面积或两者的差异。 5.5 弯曲强度试验提供了材料在管道横向荷载引起的应力下的强度和变形信息。非均匀但单轴应力状态在这些类型的测试中是固有的，任何非线性应力应变行为的后续评估必须考虑CMC在多轴应力下的不对称和各向异性行为。这种非线性行为可能是累积损伤过程的结果（例如，基体开裂、基体/纤维脱粘、纤维断裂、分层等）。 )这可能受测试模式、测试速率、处理效果或环境影响。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，可以通过本试验方法中概述的足够快的速度进行试验来最小化。 5.6 从特定材料或零件的选定部分或两者中制作成标准尺寸的试样的弯曲强度测试结果可能不能完全代表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行为。 5.7 出于质量控制目的，鉴于主要加工条件和加工后热处理，从标准抗弯强度试样得出的结果可被视为指示材料的响应。 5.8 CMC的弯曲行为和弯曲强度取决于其固有的断裂阻力、缺陷的存在、损伤累积过程或其组合。 强烈建议对断裂面和断口进行分析，尽管这超出了本试验方法的范围。

1.1 This test method covers the determination of flexural strength, including stress-strain response, under monotonic loading of continuous fiber-reinforced advanced ceramic tubes at ambient temperature. This test method addresses tubular test specimen geometries, test specimen/grip fabrication methods, testing modes (force, displacement, or strain-control), testing rates (force rate, stress rate, displacement rate, or strain rate), and data collection and reporting procedures. 1.2 In this test method, an advanced ceramic composite tube/cylinder with a defined gage section and a known wall thickness is subjected to four-point flexure while supported in a four-point loading system utilizing two force-application points spaced an inner span distance that are centered between two support points located an outer span distance apart. The applied transverse force produces a constant moment in the gage section of the tube and results in uniaxial flexural stress-strain response of the composite tube that is recorded until failure of the tube. The flexural strength and the flexural fracture strength are determined from the resulting maximum force and the force at fracture, respectively. The flexural strains, the flexural proportional limit stress, and the flexural modulus of elasticity in the longitudinal direction are determined from the stress-strain data. Note that flexural strength as used in this test method refers to the maximum tensile stress produced in the longitudinal direction of the tube by the introduction of a monotonically applied transverse force, where ‘monotonic’ refers to a continuous, nonstop test rate without reversals from test initiation to final fracture. The flexural strength is sometimes used to estimate the tensile strength of the material. 1.3 This test method is intended for advanced ceramic matrix composite tubes with continuous fiber reinforcement: unidirectional (1D, filament wound and tape lay-up), bidirectional (2D, fabric/tape lay-up and weave), and tridirectional (3D, braid and weave). These types of ceramic matrix composites can be composed of a wide range of ceramic fibers (oxide, graphite, carbide, nitride, and other compositions) in a wide range of crystalline and amorphous ceramic matrix compositions (oxide, carbide, nitride, carbon, graphite, and other compositions). This test method may also be applicable to some types of functionally graded tubes such as ceramic fiber-wound tubes comprised of monolithic advanced ceramics. It is not the intent of this test method to dictate or normalize material fabrication including fiber layup or number of plies comprising the composite, but to instead provide an appropriate and consistent methodology for discerning the effects of different fabrication or fiber layup methods on flexural behavior of resulting tubular geometries. 1.4 This test method does not directly address discontinuous fiber-reinforced, whisker-reinforced, or particulate-reinforced ceramics, although the test methods detailed here may be equally applicable to these composites if it can be shown that these materials display the damage-tolerant behavior of continuous fiber-reinforced ceramics. 1.5 The test method is applicable to a range of test specimen tube geometries based on the intended application that includes composite material property and tube radius. Therefore, there is no “standard” test specimen geometry for a typical test setup. Lengths of the composite tube, lengths of the inner span, and lengths of the outer span are determined so as to provide a gage length with uniform bending moment. A wide range of combinations of material properties, tube radii, wall thicknesses, tube lengths, and lengths of inner and outer spans section are possible. 1.5.1 This test method is specific to ambient temperature testing. Elevated temperature testing requires high-temperature furnaces and heating devices with temperature control and measurement systems and temperature-capable testing methods that are not addressed in this test method. 1.6 This test method addresses tubular test specimen geometries, test specimen preparation methods, testing rates (that is, induced applied moment rate), and data collection and reporting procedures in the following sections: Scope Section 1 Referenced Documents Section 2 Terminology Section 3 Summary of Test Method Section 4 Significance and Use Section 5 Interferences Section 6 Apparatus Section 7 Hazards Section 8 Test Specimens Section 9 Test Procedure Section 10 Calculation of Results Section 11 Report Section 12 Precision and Bias Section 13 Keywords Section 14 Appendixes Overview of Flexural Test Configurations Appendix X1 Fixtures with Cradles Appendix X2 1.7 Values expressed in this test method are in accordance with the International System of Units (SI) and IEEE/ASTM SI 10 . 1.8 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 . 1.9 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 may be used for material development, material comparison, quality assurance, characterization, and design data generation. 5.2 Continuous fiber-reinforced ceramic composites (CFCCs) may be composed of continuous ceramic-fiber directional (1D, 2D, and 3D) reinforcements which are often contained in a fine-grain-sized (<50 µm) ceramic matrix with controlled porosity. Usually these composites have an engineered thin (0.1 to 10 µm) interface coating on the fibers to produce crack deflection and fiber pull-out. 5.3 CFCC components have distinctive and synergistic combinations of material properties, interface coatings, porosity control, composite architecture (1D, 2D, and 3D), and geometric shape that are generally inseparable. Prediction of the mechanical performance of CFCC tubes (particularly with braid and 3D weave architectures) may not be possible by applying measured properties from flat CFCC plates to the design of tubes. This is because fabrication/processing methods may be unique to tubes and not replicable to flat plates, thereby producing compositionally similar but structurally and morphologically different CFCC materials. In particular, tubular components comprised of CFCC material form a unique synergistic combination of material, geometric shape, and reinforcement architecture that is generally inseparable. In other words, prediction of mechanical performance of CFCC tubes generally cannot be made by using properties measured from flat plates. Strength tests of transversely loaded CFCC tubes provide information on mechanical behavior and strength for a material subjected to a uniaxial, nonuniform stress. 5.4 Unlike monolithic advanced ceramics that fracture catastrophically from a single dominant flaw, CMCs generally experience “graceful” fracture from a cumulative damage process. Therefore, while the volume of material subjected to a nonuniform, uniaxial flexural stress for transversely loaded tube test may be a significant factor for determining matrix cracking stress, this same volume may not be as significant a factor in determining the ultimate strength of a CMC. However, the probabilistic nature of the strength distributions of the brittle matrices of CMCs requires a statistically significant number of test specimens for statistical analysis and design. Studies to determine the exact influence of test specimen volume on strength distributions for CMCs have not been completed. It should be noted that tensile flexural strengths obtained using different recommended test specimens with different volumes of material in the gage sections may be different due to these volume effects. Practice C1683 provides guidance on the scaling of statistical parameters for strength to account for differences in effective volume, effective area, or both. 5.5 Flexural strength tests provide information on the strength and deformation of materials under stresses induced from transverse loading of tubes. Nonuniform but uniaxial stress states are inherent in these types of tests, and subsequent evaluation of any nonlinear stress-strain behavior must take into account the asymmetric and anisotropic behavior of the CMC under multiaxial stressing. This nonlinear 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 effects. Some of these effects may be consequences of stress corrosion or subcritical (slow) crack growth that can be minimized by testing at sufficiently rapid rates as outlined in this test method. 5.6 The results of flexural strength tests of test specimens fabricated to standardized dimensions from a particular material or selected portions of a part, or both, may not totally represent the strength and deformation properties of the entire, full-size end product or its in-service behavior in different environments. 5.7 For quality control purposes, results derived from standardized flexural strength test specimens may be considered indicative of the response of the material from which they were taken for, given primary processing conditions and post-processing heat treatments. 5.8 The flexural behavior and flexural strength of a CMC are dependent on its inherent resistance to fracture, the presence of flaws, damage accumulation processes, or combinations thereof. Analyses of fracture surfaces and fractography, though beyond the scope of this test method, are highly recommended.