1.1 本试验方法包括在室温下使用方形、矩形或圆柱形梁在三点载荷下测定制造的碳和石墨制品的弯曲强度。 1.2 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 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。 1.4 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====== 4.1 该测试方法为材料开发、质量控制、表征和设计数据生成提供了一个框架。如实验室间研究所示，用户需要评估该方法对特定材料和预期用途的适用性。 4.2 该试验方法确定了在三点弯曲中具有简单梁几何形状的石墨试样上的最大载荷，并为计算环境温度和环境条件下的弯曲强度提供了一种方法。 4.3 弯曲应力是基于简单梁理论计算的，假设材料是各向同性和均匀的，拉伸和压缩的弹性模量相同，并且材料是线性弹性的。对于大晶粒材料，最小试样尺寸应明显大于最大晶粒尺寸（见指南 D7775 ). 4.4 一组试样的弯曲强度受与试验程序相关的几个参数的影响。这些因素包括加载速率、测试环境、样本尺寸、样本制备和测试夹具。应选择试样尺寸和夹具，以减少因材料可变性或试验参数（如试样表面的摩擦和不平行）而产生的误差。 4.5 人造石墨或碳材料的弯曲强度取决于其固有的抗断裂能力以及缺陷的大小和严重程度。 这些变化会导致试样样本的测试结果自然分散。尽管断裂表面的断口分析超出了本标准的范围，但强烈建议用于所有目的，尤其是当数据将用于实践中讨论的设计时 C1239 和 C1322 . 4.6 三点测试配置仅使试样的一小部分暴露在最大应力下。因此，三点弯曲强度可能远大于四点弯曲强度。三点弯曲有一些优点。 它使用更简单的测试夹具，允许小样本测试和断裂韧性测量。然而，四点弯曲是首选，并建议用于大多数表征目的。

1.1 This test method covers determination of the flexural strength of manufactured carbon and graphite articles using a square, rectangular or cylindrical beam in three-point loading at room temperature. 1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.3 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. 1.4 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 ====== 4.1 This test method provides a framework for material development, quality control, characterization, and design data generation purposes. The user needs to assess the applicability of the method on the specific material and for the intended use, as shown by the interlaboratory study. 4.2 This test method determines the maximum loading on a graphite specimen with simple beam geometry in three–point bending, and it provides a means for the calculation of flexural strength at ambient temperature and environmental conditions. 4.3 The flexure stress is computed based on simple beam theory with assumptions that the material is isotropic and homogeneous, the moduli of elasticity in tension and compression are identical, and the material is linearly elastic. For materials with large grains, the minimum specimen dimension should be significantly larger than the maximum grain size (see Guide D7775 ). 4.4 Flexural strength of a group of test specimens is influenced by several parameters associated with the test procedure. Such factors include the loading rate, test environment, specimen size, specimen preparation, and test fixtures. Specimen sizes and fixtures should be chosen to reduce errors due to material variability or testing parameters, such as friction and non-parallelism of specimen surfaces. 4.5 The flexural strength of a manufactured graphite or carbon material is dependent on both its inherent resistance to fracture and the size and severity of flaws. Variations in these cause a natural scatter in test results for a sample of test specimens. Fractographic analysis of fracture surfaces, although beyond the scope of this standard, is highly recommended for all purposes, especially if the data will be used for design as discussed in Practices C1239 and C1322 . 4.6 The three-point test configuration exposes only a very small portion of the specimen to the maximum stress. Therefore, three-point flexural strengths are likely to be much greater than four-point flexural strengths. Three-point flexure has some advantages. It uses simpler test fixtures, allowing small specimen testing and fracture toughness measurements. However, four-point flexure is preferred and recommended for most characterization purposes.